ADDIS ABABA UNIVERSITY ADDIS ABABA INSTITUTE OF TECHNOLOGY SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING
Early Age Thermal Behavior of Bagasse Ash Concrete Under Different Ambient Temperatures
By Amanuel Bersisa July, 2019 Addis Ababa
A Thesis in Structural Engineering
A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science
The undersigned have examined the thesis entitled “Early Age Thermal Behavior of
Bagasse Ash Concrete Under Different Ambient Temperatures” presented by Amanuel
Bersisa, a candidate for the degree of Master of Science and hereby certify that it is worthy of acceptance.
Dr. - Ing. Adil Zekeria
Advisor Signature Date
Dr. Esayas G/Youhannes
Internal Examiner Signature Date
Dr. - Ing. Girma Zerayouhannes
External Examiner Signature Date
Dr. - Ing. Henok Fikre
Chair Person Signature Date
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UNDERTAKING
I confirm that research work titled “Early Age Thermal Behavior of Bagasse Ash Concrete under Different Ambient Temperatures” is my own work. The work has not been presented elsewhere for assessment. Where material has been used from other sources, it has been properly acknowledged / referred.
Amanuel Bersisa
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ABSTRACT
Bagasse ash can be optimized as a partial cement replacing material in a concrete mixture. Other than guaranteeing mechanical properties, this pozzolana could be used as a thermal retarder for mass concrete placement, despite the fact that its property was not examined under various ambient temperatures. This research aims at studying the early age thermal and mechanical properties of bagasse ash concrete under different ambient temperatures. A semi-adiabatic temperature rise data of four different concrete mixtures (containing pure Portland cement, 6.5%, 13% and 20% dosage of bagasse ash by volume) are determined. Insulated concrete specimens of size 30*30*40cm3 were cast and the internal heat of hydration was measured at three different locations for every 30 minutes of interval. For simulating different ambient temperatures, a chamber has been constructed in the AAiT material laboratory. The temperature chamber is capable of simulating average ambient temperatures of 25.150, 35.540 and 43.770 C.
As the experimental outcomes indicate, there is reduction in early age compressive, splitting tensile, and flexural strength of concrete containing different dosages of bagasse ash. On the other hand, enhancement of strength is observed in bagasse ash concrete specimens at late age testing (with exception of 20% replacement level). The laboratory testing program revealed that, the presence of bagasse ash in the concrete mixture shifts temperature rise-time curve, reduces the total heat of hydration and decreases the thermal gradient in the specimens. Moreover, the total heat of hydration of all mixtures was significantly influenced as the ambient temperature increased, but mixtures containing bagasse ash show slower heat liberation rate relative to the control group.
Heat of hydration and thermal cracking risk were also simulated using Hacon-3 finite element software. The FES results show a good agreement with the real measurement in temperature gauges. The presence of bagasse ash in concrete up to 13% decreases the cracking risk. However, incorporating bagasse ash at a higher dosage could retard the strength development and consequently escalates the risk of cracking. This investigation proves, the main driving force that controls early age cracking risk depends on both strength development and heat liberation of concrete.
Key words: Bagasse ash, Semi-adiabatic temperature rise, Temperature chamber, Heat of hydration, Ambient temperature, Thermal gradient, Thermal cracking risk.
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ACKNOWLEDGMENTS
I would first like to take this opportunity to thank God for being my strength and guide in writing this thesis. I express my deepest gratitude to my thesis advisor Dr. - Ing. Adil Zekeria for devoting much time to consult, guide and read my work over and over again. Your assistance on both research as well as on my career have been indispensable.
Beside my advisor, the door to Dr. Esayas G.Youhannes office was always open whenever I had a question about my research work; hence, I am very thankful for his unconditional cooperation. I would also like to thank AAiT material laboratory staffs and experts from different field of study for partaking in this research.
Ethiopian road authority is playing a vital role in producing educated manpower by sponsoring educational programs. Therefore, I would like to thank ERA for sponsoring my MSc. program collaborating with AAiT. Finally, yet importantly, I would like to thank my mother: Seblewongle Dejenie for supporting me spiritually throughout my life.
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TABLE OF CONTENTS
ABSTRACT...... IV
ACKNOWLEDGMENTS ...... V
TABLE OF CONTENTS ...... VI
LIST OF TABLES ...... IX
LIST OF FIGURES ...... X
CHAPTER 1 INTRODUCTION ...... 1
1.1 MOTIVATION ...... 1 1.2 RESEARCH NEED ...... 2 1.3 OBJECTIVES AND SCOPE OF RESEARCH ...... 3 1.4 SCIENTIFIC APPROACH ...... 4 1.5 ORGANIZATION OF THESIS...... 4 CHAPTER 2 LITERATURE REVIEW ...... 5
2.1 CEMENT HYDRATION AND HEAT EVOLUTION ...... 5 2.1.1 Hydration of Ordinary Portland Cement ...... 5
2.1.2 Hydration of Cement with Supplementary Admixtures ...... 6
2.1.3 Factors That Influence Cement Hydration and Heat Evolution ...... 7
2.2 MASS CONCRETE AND THERMAL CRACKING ...... 9 2.2.1 Definition of Mass-Concrete ...... 9
2.2.2 Thermal Cracking ...... 10
2.2.3 Mitigation Strategies of Thermal Cracking ...... 10
2.3 BAGASSE ASH AND PERVIOUS STUDY ...... 12 2.3.1 Bagasse Ash ...... 12
2.3.2 Abundance of Bagasse Ash in Ethiopia...... 12
2.3.3 Previous Works on Bagasse Ash Concrete ...... 13
2.3.4 Chemical Composition of Bagasse Ash ...... 14
CHAPTER 3 MATERIAL AND METHODS ...... 15
3.1 MATERIAL ...... 15 3.1.1 Aggregate ...... 15
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3.1.2 Cement ...... 18
3.1.3 Bagasse Ash ...... 18
3.1.4 Water ...... 22
3.2 METHODS ...... 22 3.2.1 Mixture Design ...... 22
3.2.2 Mixing, Vibrating, and Curing Condition ...... 23
3.2.3 Test Setup and Procedure ...... 25
CHAPTER 4 RESULT AND DISCUSSION ...... 30
4.1 FRESH CONCRETE PROPERTIES...... 30 4.2 HARDENED CONCRETE PROPERTIES ...... 31 4.2.1 Compressive Strength ...... 31
4.2.2 Splitting Tensile Strength ...... 32
4.2.3 Flexural Strength ...... 34
4.3 EARLY AGE THERMAL PROPERTIES ...... 36 4.3.1 Effect of Ambient Temperature on Heat Evolution ...... 38
4.3.2 The Effect of Bagasse Ash on Early Age Heat Evolution ...... 46
CHAPTER 5 FINITE ELEMENT MODELING ...... 53
5.1 MODEL DESCRIPTION ...... 53 5.2 ABOUT HACON-3 FES ...... 53 5.3 INPUT PARAMETERS ...... 53 5.3.1 Specific Heat Capacity ...... 54
5.3.2 Thermal Conductivity ...... 54
5.3.3 Coefficient of Thermal Expansion ...... 54
5.3.4 Thermal Diffusivity ...... 54
5.3.5 Total Heat of Hydration ...... 54
5.4 MODELING ...... 55 5.4.1 Geometry ...... 55
5.4.2 Material ...... 56
5.4.3 Boundary Conditions ...... 57
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5.4.4 Analysis ...... 57
5.5 RESULT AND DISCUSSION ...... 57 5.5.1 Hydration Heat Simulation ...... 57
5.5.2 Cracking Risk Simulation ...... 60
5.5.3 Influence of Insulation on Thermal Gradient ...... 62
5.5.4 Influence of Specimen Size on Thermal Gradient ...... 65
CHAPTER 6 CONCLUSION AND RECOMMENDATION...... 66
6.1 CONCLUSION ...... 66 6.2 RECOMMENDATIONS FOR FUTURE WORK ...... 67 REFERENCE ...... 68
APPENDIX A ...... 75
APPENDIX B ...... 79
APPENDIX C ...... 84
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LIST OF TABLES
Table 2.1 Heat Evolution of Compounds (Bogue, 1929) ...... 7 Table 3.1 Summary Physical Property of Fine Aggregate ...... 15 Table 3.2 Gradation of Fine Aggregate ...... 16 Table 3.3 Summary Physical Property of the Coarse Aggregate ...... 17 Table 3.4 Gradation of the Coarse Aggregate ...... 17 Table 3.5 Gradation of Bagasse Ash and Cement ...... 19 Table 3.6 Chemical Property of Cement and Bagasse Ash ...... 21 Table 3.7 Quantity of Material Required Per Metric Cube of Concrete ...... 22 Table 3.8 Quantity of Bagasse Ash for Each Replacement Level ...... 23 Table 4.1 Average Slump Value for Each Mixture ...... 30 Table 4.2 Average Compressive Strength ...... 31 Table 4.3 Average Splitting Tensile Strength of Concrete ...... 33 Table 4.4 Average Flexural Strength ...... 35 Table 4.5 Peak Temperature in Concrete Specimens ...... 38 Table 5.1 Ultimate Heat of Hydration for Different Mixtures ...... 55
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LIST OF FIGURES
Figure 1.1 Early Age Thermal Cracking on a Massive Foundation ...... 2 Figure 2.1 Temperature Rise for Mass Concrete Under Adiabatic Condition ...... 8 Figure 2.2 The Effect of Placing Temperature on Adiabatic Temperature Rise ...... 9 Figure 2.3 Embedded Cooling Pipes ...... 11 Figure 2.4 Sugarcane, Sugarcane Bagasse, and Bagasse Ash Respectively ...... 12 Figure 2.5 Bagasse Deposit at Metehara Sugar Factory ...... 13 Figure 3.1 Gradation of Local Fine Aggregate ...... 16 Figure 3.2 The Gradation of Local Coarse Aggregate ...... 18 Figure 3.3 Bagasse Ash before and after Sieving ...... 19 Figure 3.4 Particle Size Distribution of Cement and Bagasse Ash ...... 20 Figure 3.5 X-Ray Diffraction Result of Local Bagasse Ash ...... 21 Figure 3.6 Measuring Slump of Fresh Concrete ...... 24 Figure 3.7 (a) Mixing Machine (b) Curing Condition ...... 24 Figure 3.8 Compressive Strength Test Setup ...... 25 Figure 3.9 Flexural Strength Test Setup ...... 26 Figure 3.10 (a) Insulated Plywood Mold (b) Location of Sensors Throughout Depth ..... 27 Figure 3.11 Demolding and Demolishing Concrete Samples ...... 28 Figure 3.12 Chamber on Progress of Construction ...... 28 Figure 3.13 Final Setup of Temperature Chamber with its Full Controlling System ...... 29 Figure 4.1 Average Compressive Strength Development ...... 32 Figure 4.2 Test Set up of Splitting Tensile Strength Test ...... 33 Figure 4.3 Splitting Tensile Strength Development ...... 34 Figure 4.4 Flexural Strength Development ...... 35 Figure 4.5 25.15º C Average Ambient Temperature History ...... 36 Figure 4.6 35.54º C Average Ambient Temperature History ...... 37 Figure 4.7 43.77º C Average Ambient Temperature History ...... 37 Figure 4.8 Temperature Profile of Control Specimen at 25.150 Ambient Temperature ... 39 Figure 4.9 Temperature Profile of Control Specimen at 35.540 Ambient Temperature ..39 Figure 4.10 Temperature Profile of Control Specimen at 43.770 Ambient Temperature. 40 Figure 4.11 Temperature Profile of Concrete Specimen Contain 6.5% BA at 25.150 Ambient Temperature ...... 40
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Figure 4.12 Temperature Profile of Concrete Specimen Contain 6.5% BA at 35.540 Ambient Temperature ...... 41 Figure 4.13 Temperature Profile of Concrete Specimen Contain 6.5% BA at 43.770 Ambient Temperature ...... 41 Figure 4.14 Temperature Profile of Concrete Specimen Contain BA 13% BA at 25.150 Ambient Temperature ...... 42 Figure 4.15 Temperature Profile of Concrete Specimen Contain 13% BA at 35.540 Ambient Temperature ...... 42 Figure 4.16 Temperature Profile of Concrete Specimen Contain 13% BA at 43.770 Ambient Temperature ...... 43 Figure 4.17 Temperature Profile of Concrete Specimen Contain 20% BA at 25.150 Ambient Temperature ...... 43 Figure 4.18 Temperature Profile of Concrete Specimen Contain 20% BA at 35.540 Ambient Temperature ...... 44 Figure 4.19 Temperature Profile of Concrete Specimen Contain 20% BA at 45.770 Ambient Temperature ...... 44 Figure 4.20 Top Temperature Profile of Different Mixture Specimens at 25.150 Ambient Temperature ...... 47 Figure 4.21 Middle Temperature Profile of Different Mixture Specimens at 25.150 Ambient Temperature ...... 47 Figure 4.22 Bottom Temperature Profile of Different Mixture Specimens at 25.150 Ambient Temperature ...... 48 Figure 4.23 Top Temperature Profile of Different Mixture Specimens at 35.540 Ambient Temperature ...... 48 Figure 4.24 Middle Temperature Profile of Different Mixture Specimens at 35.540 Ambient Temperature ...... 49 Figure 4.25 Bottom Temperature Profile of Different Mixture Specimens at 35.540 Ambient Temperature ...... 49 Figure 4.26 Top Temperature Profile of Different Mixture Specimens at 43.770 Ambient Temperature ...... 50 Figure 4.27 Middle Temperature Profile of Different Mixture Specimens at 43.770 Ambient Temperature ...... 50 Figure 4.28 Bottom Temperature Profile of Different Mixture Specimens at 43.770 Ambient Temperature ...... 51 xi
Figure 5.1 Meshing and Element Property ...... 56 Figure 5.2 Material Modeling Tab in Hacon-3 ...... 56 Figure 5.3 Assigned Boundary Conditions on Specimen Surface ...... 57 Figure 5.4 Temperature Profile of the Control Group at 25.150 Ambient Temperature ... 58 Figure 5.5 Bottom Temperature Profile at Ambient Temperature 25.150 C ...... 58 Figure 5.6 Bottom Temperature Profile at Ambient Temperature of 35.540 C ...... 59 Figure 5.7 Bottom Temperature Profile at Ambient Temperature of 43.770 C ...... 59 Figure 5.8 Cracking Risk at Ambient Temperature of 25.150 ...... 60 Figure 5.9 Cracking Risk at Ambient Temperature of 35.540 ...... 61 Figure 5.10 Cracking Risk at Ambient Temperature of 43.770 ...... 61 Figure 5.11Temperature Profile of Insulated Concrete at 25.150 Ambient Temperature (Size: 0.3m*0.4m) ...... 62 Figure 5.12 Temperature Profile of not Insulated Concrete at 25.150 Ambient Temperature (Size: 0.3m*0.4m) ...... 63 Figure 5.13 Temperature Profile of Insulated Concrete at 25.150 Ambient Temperature (Size: 3m*4 m) ...... 63 Figure 5.14 Temperature Profile of not Insulated Concrete at 25.150 Ambient Temperature (Size: 3m*4 m) ...... 64 Figure 5.15 Thermal Gradient of Insulated and Concrete without Insulation ...... 64 Figure 5.16 Thermal Gradient of Different Size Concrete Specimens ...... 65
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ABBREVIATIONS, SIGNS, AND SYMBOLS
A.S.L. Above Sea Level
AAiT Addis Ababa Institute of Technology
ACI American Concrete Institute
ASTM American Standard Testing Material
ASCE American Society of Civil Engineering
C–S–H Calcium Silicate Hydrate
C2S Di-Calcium-silicate
C3S Tri-Calcium-Silicate
C4AF Tetra-Calcium-Alumino-Ferrite
C3A Tri-Calcium Aluminate
EMA Ethiopian Mapping Authority
FES Finite Element Software
FEM Finite Element Method
GGBFS Ground Granulated Blast Furnace Slug
GOE Government of Ethiopia
LOI Loss of Ignition
MPa Mega Pascal
NMA National Meteorological Agency
NRMCA National Ready Mix Concrete Association
PC Portland Cement
SCM Supplementary Cementitious Materials
SCB Sugarcane Bagasse
SCBA Sugarcane Bagasse Ash
USDA United States Department of Agriculture
XRD X-Ray Diffraction
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
CHAPTER 1 INTRODUCTION
1.1 MOTIVATION
With amplified environmental awareness, the recycling of industrial byproducts has become an attractive alternative for disposal. Besides disposal management, several reports show that utilization of waste material like plastics, coal bottom ash, bagasse ash, coal fly ash, cement kiln dust, etc. in concrete enhances its texture, strength and durability. Bagasse is among the industrial by-product found abundantly in Ethiopia. Off course, there is some traditional way of using bagasse ash as a fertilizer for the production of crops, but it can be utilized for other purposes as well. According to studies, bagasse ash can partially replace cement due to its pozzolana behavior. Using this type of advantage is quite crucial in order to minimize environmental pollution resulted from the emission of CO2 when producing cement. Besides the abundance of bagasse ash disposed of existing sugar factories, other factories of different production capacity are under construction along with the various irrigation projects. By 2020 the bagasse ash production (estimated amount of 1.9Million ton) from the local factories will reach into a figure around 16.01% of the over- all cement need of the time. (Geremewu, 2017) Application of pozzolana material in concrete hinge on the hydration of cement and possibly modifies the reaction momentum. As hydration is an exothermic reaction, it will possess heat on concrete sections. If the volume concrete section is large, hydration heat accumulated at the interior of the structure is not easy to be lost so that, the temperature inside the concrete rise. The temperature difference between the inner and surface concrete will produce a thermal gradient. At early age, thermal dilution will impose compressive stress on the concrete section, which result formation of surface cracks. Through time the concrete surface cools and tries to shrink; therefore, the specimen will be under tension. When the tensile strength of the concrete is not enough to resist the tensile stress, through crack will be produced. (Neville, 2011; Bobko et al., 2015)
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
Figure 1.1 Early Age Thermal Cracking on a Massive Foundation (https://www.concretebridgeviews.com)
Factors such as ambient temperature affect the rate of hydration and heat evolution of both pozzolana and cementitious materials. Therefore, studies should have to be carried out on different environmental conditions before one can use pozzolana and cement in real life construction works. According to NMA (2007), the temperature which covers a wide range of land in Ethiopia, varies from 200 to 450 Celsius. Though wide coverage of temperature and humidity range of Ethiopia, papers done on bagasse ash concrete are conducted on specific target temperature, which makes the applicability of the studies not comprehensive.
1.2 RESEARCH NEED
Scientists have been documenting climate-related shifts due to the emanation of CO2 and disposal of a waste products. Production of cement is the third-largest source of anthropogenic emission of carbon dioxide, in which it covers up to 5% of the total amount (Raja, 2014; Mikulclc et al., 2013). Besides the increment of carbon dioxide due to cement production, the demand and cost of this construction material is inflating (Joshua et al., 2018). Counting the odds constructions are not altered for a while, as it is crucial for human development. Through all this, the utilization of supplementary cementitious materials
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures from the by-product of industries come in to picture. The use of SCMs conserves energy and has environmental benefits due to reduction in carbon dioxide emission since the manufacturing of cement declines. Furthermore, recycling of SCMs help to regulate an abundance of industrial by-products (Abdulkadir et al., 2014; Awad et al., 2017) Among SCMs, Bagasse ash is the earlier one. Researches have been giving a clue for utilizing bagasse ash as partial replacement for cement to a certain optimum level. As per previous studies, Cement can be replaced by 10% to 15% of bagasse ash with an insured good mechanical property of concrete. Although there is a good beginning, the early age thermal properties, shrinkage, long-term and early age mechanical properties of concrete containing this pozzolana are not fully addressed. Gremew (2017) had tried to investigate the application of bagasse ash for rigid pavement. The research result was overwhelming and gives a clue that bagasse ash can be used as a thermal retarder. As a part of consecutive research, further study should be carried out to investigate the early age thermal property of bagasse ash concrete under different ambient temperature.
1.3 OBJECTIVES AND SCOPE OF RESEARCH
The general objective of this study is investigating the early age thermal behavior of bagasse ash concrete under different ambient temperatures. Furthermore, the influence of Bagasse ash on the development of early age mechanical properties (compressive and tensile strength) of concrete is also a part of this study. The main scope is defined as follows: - • To review the existing knowledge of Cement hydration, pozzolana reaction, thermal cracking and utilization of bagasse ash in concrete. • Performing comprehensive experimental programs to investigate the influence bagasse ash on strength development of young concrete. • Undertaking experimental investigations to study the effect of ambient temperatures on the heat evolution of concrete containing bagasse ash and validating the outcomes using finite element software.
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
1.4 SCIENTIFIC APPROACH
The first crucial step was a critical state-of-art report. Information’s and previous studies are structured in a compressive way in order to find gaps and supportive feedbacks. Preceding step was designing of experimental programs and preparation of experimental setups. Experiment programs are classified into two major part. The first part includes chemical and physical characterization of construction materials. The second part incorporates early age thermal and mechanical properties investigation.
For major experimental program, 40*30*30 cm3 concrete samples were used to measure early age heat evolution using thermocouples. The specimens were insulated using Styrofoam in five directions. The upper part was left uninsulated for examining the effect of ambient temperature on the response concrete specimens. For simulating different ambient temperatures, Chamber has been constructed at AAiT material laboratory.
1.5 ORGANIZATION OF THESIS
CHAPTER 1 of this paper states the motivation for the study. The research needs, research goals and the corresponding scientific approach is emphasized in this chapter.
CHAPTER 2 of this report provides thorough discussion about cement hydration, heat evolution, influence factor on the heat of hydration, abundance, and application of bagasse ash on concrete, etc.
CHAPTER 3 documents physical and chemical characterization of construction materials. The adopted research methods and test setups to achieve the research goals are also a part of this section.
CHAPTER 4 present major experimental program results. The mechanical properties and heat evolution of different concrete mixture were discussed based on scientific explanation.
CHAPTER 5 deals with finite element modeling for prediction of early age thermal crack risk. The modeling issues, input parameters and analyses results are well documented.
CHAPTER 6 offers conclusions and recommendations for future works.
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
CHAPTER 2 LITERATURE REVIEW
2.1 CEMENT HYDRATION AND HEAT EVOLUTION
When water and cement are mixed, the constituent compounds undergo a chemical reaction termed hydration, which results in new compounds called hydration product.
Among the cement constitutes both C3S and C2S react with water to produce an amorphous calcium silicate hydrate known as C–S–H gel, which is the main glue that binds the sand and coarse aggregate particles together in concrete. (Kim, 2010, Perumal et al., 2016; Neville, 2011) Cement hydration is an exothermic reaction, which produces a high amount of heat. The amount of heat generated in the concrete depends on different factors including cement type, chemical composition, casting temperature and ambient temperature. (Lagundžija and Thiam, 2017; Meadows, 2007)
2.1.1 Hydration of Ordinary Portland Cement Ordinary Portland cement is composed largely of four types of minerals: alite (C3S), belite
(C2S), aluminate (C3A), and alumino-ferrite (C4AF). When the various compounds are present all together in cement, their rates of hydration will be affected by compound interactions.
Tri-calcium-silicate (C3S) or alite is responsible for the major engineering properties of concrete. The Portland cement clinker may contain about 40–60% C3S (Neville, 2011).
The hydration reaction of C3S is exothermic and can be expressed by stoichiometric Equation 2.1 (Kim, 2010). 2CS 11 H CSHCSH ( - - ) 3 CH (CalciumHydroxide)...... (2.1) 3 3 2 8 2CS2 9 H CSHCSH 3 2 8 ( - - ) CH (CalciumHydroxide)...... (2.2)
Di-calcium-silicate (C2S) or belite is another important component of cement clinker. The
PC clinker may contain about 12–30% C2S (Neville, 2011). Like C3S, the hydration reaction of C2S is also exothermic, which can be expressed by the stoichiometric equation as shown in Equation 2.2. The principal hydration product alite and belite is calcium silicate hydrate (C-S-H) and calcium hydroxide.
The PC clinker may contain 3–14% tri-calcium-aluminate (C3A) or aluminate. Even if the amount of tri-calcium aluminate (C3A) occurred in cement is small, the relationship of this
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures constitute with other compounds should have to be a point of interest. The reaction of this compound at pure state is very volatile and will result a flash set. Since C3A reacts with water immediately, in order to avoid flash setting, gypsum is added (Neville, 2011). The hydration products of C3A are commonly formed of ettringite in the first stage (Equation 2.3) and mono-sulfo-aluminate later as shown on Equation 2.4 (Kim, 2010). Tri-calcium aluminate (C3A) contributes little to the strength of cement paste. 2C A 3 CSH 26 H C AS H (ettringite )...... (2.3) 3 2 6 3 32 C3 A C 6 AS 3HHCA 32 4 3 4SH 12 (mono- sulfo- alu min ate )...... (2.4)
Researches show that, the hydration of C3A is retarded by the presence of Ca(OH)2, which is liberated from the hydration of C3S. The phenomenon occurs because Ca(OH)2 will form a proactive layer on the surface of un-hydrated grains of C3A. The main purpose of
C3A addition on the cement is in facilitating the burning process of cement clinkers by using it as a heat flux. (Neville, 2011)
Tetra-calcium-alumino-ferrite (C4AF) or ferrite is a ternary phase (three component system) occurring in cement clinker, resulting from the solid solution of calcium aluminate and calcium ferrite (C2A-C2F). The PC clinker may contain around 7%–16% C4AF. The hydration of tetra-calcium alumino-ferrite (C4AF) is slower and involve less heat. Two possible hydrates can form depending on the availability of gypsum (Equations 2.5 & 2.6). (Kim, 2010) CAF 3 CSH 21 H CAFSH ( , ) ( FAH , ) ...... (2.5) 4 2 6 3 32 3 CAF4 CAFSH 6 ( , ) 3 32 7 H 3 CAFSH 4 ( , ) 12 ( FAH , ) 3 ...... (2.6) The amount of gypsum added in concrete should have to be at the optimum level. Further increment in gypsum content will leads expansion of concrete and consequent disruption on the setting of cement paste. (Portland cement Association, 1997; Lagundžija and Thiam, 2017)
2.1.2 Hydration of Cement with Supplementary Admixtures In addition to the former hydration process, the presence of admixture causes different types of chemical reaction. Especially the addition of pozzolana material in cement have a great interaction with calcium hydroxide Ca(OH)2. Calcium hydroxide is formed as tri and di-calcium silicates react with water. The presence of calcium hydroxide as by-product enables secondary hydration by adding pozzolana to the system.
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
SiO/ Al 2 O Ca OH C - S - H ……...... (2.7) 23 2 As shown in Equation 2.7, additional C-S-H gel can be formed by adding reactive admixture on the formal cement hydration. (Siddique et al., 2011; Kim, 2010; Perumal et al., 2016)
2.1.3 Factors That Influence Cement Hydration and Heat Evolution The rate and amount of heat liberated during hydration greatly depends on cement type, chemical composition, physical properties of cement, water/cement ratio, the presence of supplementary cementitious material, and curing conditions.
2.1.3.1 Chemical Composition of Cement The hydration heat of each cement compound is different. The total heat of hydration that compounds possess after complete hydration according to Bogue (1929) is summarized in Table 2.1.
Table 2.1 Heat Evolution of Compounds (Bogue, 1929) Heat Evolution after Rate of Reaction with Compound Complete Hydration(J/g) Water Bogue(1947)
C3S 500 "Medium"
C2S 260 "Slow"
C3A 866 "Fast"
C4AF 420 "Medium"
Order of hydration rate during the first few days is approximately C3A > C3S > C4AF >
C2S. (Bogue, 1929; Kim, 2010)
2.1.3.2 Type of Cement The amount of heat generated by each class of cement varies according to the proportion of its respective compounds, as each has different heat of hydration. Figure 2.1 shows the heat generation rates for different types of cement under adiabatic conditions.
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
Figure 2.1 Temperature Rise for Mass Concrete Under Adiabatic Condition of Different Cement Type, (Containing 223kg/m3 of Cement) (ACI 207, 1995).
2.1.3.3 Fineness Fineness represents the material available for making contact with water so that it hydrates. Higher fineness provides a greater surface area to be wetted, which results in acceleration of the reaction between cement and water. This increases the rate of heat liberation at early ages, but may not influence the total amount of heat developed over several weeks (Portland cement Association, 1997). Wang, (2014) had studied the effect of Blaine fineness in the heat generation of cement hydration. The research shows that heat generation from hydration of coarser cement during early age was lower because of slower cement hydration.
2.1.3.4 Water/Cement Ratio According to Kim (2010) for full hydration, the range of water to cement ratio should be 0.4-0.42. Since the hydration is the major source of heat, it will upsurge for an increase in water to cement ratio (Portland cement Association, 1997). According to Wang et al. (2014), the heat of hydration at early age is higher for lower water to cement ratio.
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
2.1.3.5 Casting and Ambient Temperature The environmental temperature is also important in determining the heat of hydration. Cement hydration at higher environmental temperature is accelerated at early ages but decelerated later on (Kim, 2010). Since seasonal change becomes significant, it should be considered on mass concrete structures, which is constructed for a long period of time.
Figure 2.2 The Effect of Placing Temperature on Adiabatic Temperature Rise (ACI 207, 1995)
2.1.3.6 Supplemental Cementitious Materials (SCMs) SCMs has been widely used as partial replacements for Portland cement. The proper use of pozzolana has advantages in reduction of a heat of hydration. The pozzolana reaction generates less heat than ordinary Portland cement because the reaction is similar to a C2S reaction. Various studies have shown that partial replacement of cement by Fly ash, GGBF Slag and Bagasse ash will significantly decrease hydration heat. (Geremew, 2017; Meadows, 2007; Parham and Chini, 2005)
2.2 MASS CONCRETE AND THERMAL CRACKING
2.2.1 Definition of Mass-Concrete According to ACI 207, Mass concrete is defined as “any volume of concrete with dimensions large enough to require that measures be taken to cope with generation of heat from hydration of the cement and attendant volume change, to minimize cracking”. The
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures other precaution for mass concrete should be taken even for a thinner section, if higher heat generating concrete mixing, higher cementitious materials content or faster hydrating mixtures is used. (NRMCA, 2009)
According to Ulm and Coussy (2001), the definition of Mass-concrete is given by hydration-heat diffusion length: the gauge length that relates thermal diffusivity and characteristics hydration time which varies with the degree of hydration and temperature. Structural concrete is then defined as Mass-concrete when the maximum distance of any point in the concrete to its nearest free surface is greater than the hydration heat diffusion length.
2.2.2 Thermal Cracking Cracking in concrete structures are two types. Crack induced due to an external load, that are included in the conventional structural design calculation, and material type resulted by temperature differential or restrained condition. Early age concrete cracking is caused by restrained volume changes (i.e. autogenous shrinkage and thermal dilation) in hardening concrete structures and it is serious threat to aesthetics, tightness, and durability. (Klemczak & Knoppik-Wróbel, 2011) During the hydration of cement, heat is generated. In thin concrete sections, the generated heat dissipates to the atmosphere relatively quickly in a way the temperature of concrete is not greatly influenced. On contrast, the temperature in thicker sections will not be lost easily, rather it will accumulate on the interior part while the temperature at the outer edges remains relatively low. The uneven temperature distribution throughout the concrete element is known a thermal gradient. It results in non-uniform volume change across the element’s cross-section, thereby inducing stresses to cause thermal cracks. (Lagundžija et al., 2017; Bobko et al., 2013; ACI 207, 1995)
2.2.3 Mitigation Strategies of Thermal Cracking
2.2.3.1 Thermal Reducing Binders Low-heat generating concrete mixtures are always a wise choice for mass concrete to minimize potential thermal problems. Low-heat binders such as class F fly ash or slag as cement replacements, and the minimum amount of total cementitious materials can greatly
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures reduce the temperature evolution when there is a thermal cracking risk. (Thomas, 1994. Belie et al, 2018)
2.2.3.2 Pre Cooling of Concrete The concrete temperature at the time of placement has a great impact on the maximum heat on concrete. Methods to precool concrete include shading and sprinkling of aggregate piles, use of chilled mix water, and replacement of mix water by ice. Efforts to cool aggregates have the most pronounced effects on the concrete heat evolution because they represent 70 to 85% of the weight of concrete. (ACI 207, 1995; Lagundžija & Thiam, 2017)
2.2.3.3 Post Cooling of Concrete Post-cooling is most effectively achieved by using embedded cooling pipes that circulate cool liquid through the concrete. The goal of this method is to lower the maximum temperature reached within the concrete and to increase its cooling period (Gajda and Vangeem, 2002). If used correctly, post cooling can be beneficial in allowing earlier removal of formwork and reducing the amount of time needed for cooling. (Bobko et al., 2013)
Figure 2.3 Embedded Cooling Pipes (http://www.newwrighthouse.blogspot.com)
2.2.3.4 Adopting Insulation Insulation or insulated formwork is often used to warm the concrete surface and reduce the temperature gradient, which in turn minimizes the potential for thermal cracking. Once the temperature difference of the internal and external surface of the concrete is not exceeded 200, thermal cracks will be insignificant (ACI 207, 1995). For most mass pours, surface insulation does not appreciably increase the maximum concrete temperature, but
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures it can significantly decrease the rate of cooling. Insulation often has to remain in place for several weeks or longer. Removing it too soon can cause the surface to cool quickly so that crack appears. (Bobko et al., 2013)
2.3 BAGASSE ASH AND PERVIOUS STUDY
2.3.1 Bagasse Ash Sugarcane is an important food crop for tropics and subtropics. It is the major raw material used for sugar production. After crushing of sugarcane in sugar mills and extraction of juice from prepared cane by milling, the discarded fibrous residual matter of cane is called bagasse. Bagasse is very commonly used as fuel in boilers in the sugar mills for cogeneration process. After burning in the cogeneration boiler, bagasse ash is collected in a baghouse filter and is disposed locally, which causes severe environmental problems. (Raja, 2014; De Belie et al, 2018). For every ten tons of sugarcane crushed, a sugar factory produces nearly three tons wet bagasse ash. The combustion yields ashes containing high amounts of unburned matter like silica and alumina oxides. Studies recommend that sugarcane bagasse ash could be used as cement replacement material to improve quality and reduce the cost of concrete. (Srivastava et al., 2015; Mahmud et al., 2018)
Figure 2.4 Sugarcane, Sugarcane Bagasse, and Bagasse Ash Respectively
2.3.2 Abundance of Bagasse Ash in Ethiopia In recent years, the government of Ethiopia (GOE) has made considerable investments for boosting the country’s capacity to produce sugar. With these investments, the GOE envisions the country becoming one of the world’s ten largest sugar producers by 2023 (USDA Foreign Agricultural Service, 2015). Collaborating existing industries with the MSc Thesis Page 12
Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures future ones, the total bagasse ash to be disposed is estimated to be 1.9 million tons per year. (Geremew, 2017)
Figure 2.5 Bagasse Deposit at Metehara Sugar Factory
2.3.3 Previous Works on Bagasse Ash Concrete Geremew (2017) studied the appliance of bagasse ash in rigid pavements. In addition to the mechanical properties testing, the heat evolution of a concrete specimens containing SCBA was measured. As it is shown in study, bagasse ash attenuates the total heat of hydration and enhanced the mechanical properties of concrete specimens. Srivastava et al. (2015) carried out experimental studies with different cement to bagasse replacement ratios for examining the mechanical properties of concrete. Low weight concrete with good mechanical properties can be assured with 10% replacement level. Furthermore, tolerating slight reduction in strength of concrete, bagasse can replace the cement up to 20%. Reddy et al. (2013) utilizes bagasse ash for enhancing the chloride and corrosion resistance of concrete. Cement has been replaced by equivalent weight of bagasse ash. Meanwhile, gypsum was used to ensure workability of a mortal. Fifteen percent of replacement level is found to be the optimum. Reddy et al. (2013) had also studied the heat liberation of mixture contain bagasse ash and found that, hydration heat of concrete specimens was reduced. According to Suliman et al., (2011), bagasse acts as a class F fly ash. The chemical composition result shows that silica-di-oxide content varies from 56.7-58.02%. On the MSc Thesis Page 13
Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures other hand, bagasse is a nonvolatile, incombustible, and thermally altered mineral. Sathiya et al. (2010) had also examined that, three-oxide component (SiO2, Al2O3, Fe2O3) found in bagasse ash were account more than 75% of the total mineral content. Moreover, the loss of ignition was within the limit as it is prescribed in the ASTM C 618-00 manual. Hailu (2012) used Wonji sugar cane factory bagasse ash for inspecting the development mechanical property of concrete containing SCBA. Volume-based replacement method was used in order to ensure the workability of the mortal and create a fixed paste volume for all replacement ratio.
2.3.4 Chemical Composition of Bagasse Ash Taking in to account chemical composition (Percentage of oxides), alkaline and loss of ignition (LOI), bagasse has been classified in either class C or F fly ash (Belie et al., 2018). One of the major factor for utilization of bagasse is the amount LOI; the non-mineral material should have not exceeded the limit proposed by standards. The unburned carbon particles in SCBA are usually the largest contributor to the loss of ignition. (Abdulkadir et al., 2014)
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CHAPTER 3 MATERIAL AND METHODS
3.1 MATERIAL
Physical and chemical characterization of construction materials conducted according to ACI and ASTM standards at AAiT material laboratory. The particular details are presented on the following sections.
3.1.1 Aggregate Aggregate is a comprehensive term, which includes fine and coarse aggregate. At least three-quarter of concrete is occupied by aggregate; it is not surprising that its quality is of considerable importance. (Neville, 2011)
3.1.1.1 Fine Aggregate Fine aggregate generally consists of natural sand or crushed stone with most particle smaller than 5mm (0.2in). The fine aggregate was collected from Legehar commercial construction material site. The sand was properly washed and packed in plastic bag for controlling its moisture content. The physical property of sand is summarized in Table 3.1& 3.2.
Table 3.1 Summary Physical Property of Fine Aggregate No. Property Standard Value
1 Silt Content Dinku. A 3.4%
2 Fineness Modules ASTM C 136-84 2.61 3 Moisture Content ASTM C 566- 84 1.62%
4 Dry Rodded Unit Weight ASTM C 29 – 97 1524.39kg/m3
5 Bulk Specific Gravity ASTM C 127 – 88 2.41
6 Absorption Capacity ASTM C 127 – 88 2.74
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Table 3.2 Gradation of Fine Aggregate Sieve Size Weight Retained Percent Cumulative Cumulative (g.) Retained (%) Retained (%) Passing (%)
4.75mm 0 0 0 100 2.36mm 30 6 6 94 1.18mm 75 15 21 79 0.6mm 130 26 47 63 0.3mm 210 42 89 11 0.15mm 45 9 98 2 Pan 10 2 100 0
According to ASTM C-33-01, the upper and lower bound of percentage cumulative passing for fine aggregate in each sieve size is specified. The local fine aggregate satisfies ASTM C-33-01 requirement. `
Gradation of Fine Aggregate 120
100 100 100 100 95 94 85 80 80 79 60 6063 50 40 30 20 25 11 10 5
% Cummulative Passing Cummulative % 0 02 9.5 4.75 2.36 1.18 0.6 0.3 0.15 Sieve Size
Local Sand Lower Uper
Figure 3.1 Gradation of Local Fine Aggregate and ASTM C-33-01 Requirement
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3.1.1.2 Coarse Aggregate Crushed rock was used as a coarse aggregate for this study. Table 3.3 & 3.4 show the physical properties of coarse aggregate.
Table 3.3 Summary Physical Property of the Coarse Aggregate No. Test Description Standard Value
1 Nominal Aggregate Size ASTM D 448 – 98 25mm
2 Moisture Content ASTM C-566- 84 0.81%
3 Bulk Unit. Wt. C 29/C 29M – 97 1641.79kg/m3
4 Dry Rodded unit wt. C 29/C 29M – 97 1598.65kg/m3
5 Absorption Capacity ASTM C 127 – 88 1.52%
6 Bulk 2.75 Specific ASTM C 127 – 88 Gravity Bulk(SSD) 2.80% Apparent 2.88
Table 3.4 Gradation of the Coarse Aggregate Sieve Weight Retained Percent Cumulative Cumulative Size(mm) (kg) Retained (%) Retained (%) Passing (%)
37.5 0 0 0 100 25 5.01 34.26 34.26 65.74 19 3.66 24.4 58.66 41.34 12.5 3.51 23.4 82.06 17.94 9 1.315 8.76 90.82 9.18 4.75 1.285 8.56 99.38 0.62 Pan 0.09 0.62 100 0
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
Figure 3.2 shows the local coarse aggregate gradation in adjacent the upper and lower boundaries according to ASTM-33-01.
Gradtion of Coarse Aggregate 120
100 10095 80 70 60 40 41.34 35 30 20 11.11 10 5 % Cummulative Passing Cummulative % 0 0.620 37.5 19 9.5 4.75 Sieve Size
Uper Lower Local C. Aggregate
Figure 3.2 The Gradation of Local Coarse Aggregate and ASTM C-33-01 Requirement
3.1.2 Cement The cement material used was Type-1 Portland cement (42.5-N) from Dangote cement factory. The chemical and physical properties of the cement were examined and reported simultaneously with bagasse ash data.
3.1.3 Bagasse Ash
3.1.3.1 Physical Properties The bagasse ash was collected from Wonji sugar factory byproduct dumping area. After bagasse ash was left to dry for certain amount of time, it was filtered using a 300-µm sieve for removing the unburned carbon particles.
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Figure 3.3 Bagasse Ash before and after Sieving
Gradation: pozzolana assets might be dependent on the fineness of bagasse ash. As long as the bagasse ash composition is fine and free from unburned carbon particles, it could ensure the early age mechanical properties of the concrete.
Table 3.5 Gradation of Bagasse Ash and Cement
Wt. of B.A Cumulative Sieve Percent Cumulative Cumulative Retained Passing of Size Retained (%) Retained (%) Passing (%) (g.) Cement (%)
150 µm 45 9.09 9.09 92.91 100 125 µm 50 10.11 19.2 80.8 97.9 75 µm 180 36.36 55.96 44.44 95.5 63 µm 65 13.13 68.69 31.31 85.8 32 µm 145 29.29 97.98 2.02 4.7 Pan 10 2.02 100 0 0
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Particle Size Distribution of Cement and B.A 120 100 92.91100 97.2 93.1 80 80.8 76.2 60 40 44.44 31.31 20 0 2.14.3 0
150 125 75 63 32 Cummulative Passing (%)Cummulative Sieve Size (µm) Cement Bgasse Ash
Figure 3.4 Particle Size Distribution of Cement and Bagasse Ash
Specific Gravity: The specific gravity of cement and bagasse ash was examined according to ASTM C188–17 standard procedures were found to be 3.15 and 2.14 respectively. The weight of bagasse ash used for volume-based replacement relays on its specific gravity.
Specific Surface Area (Blaine Air-Permeability Test): The specific area of the bagasse ash is determined according to ASTM 2 204-00 using Blaine air permeability apparatus. The specific area of bagasse ash is found to be 3177.3 cm2/g.
3.1.3.2 Chemical Properties X-Ray Diffraction: XRD is a technique used to determine the mineral properties of a crystalline solid. When a solid is exposed to X-Rays of a particular wavelength, layers of atoms diffract and produce a pattern of peaks, which characterize the minerals present in the material (Cullity, 1977).
Silica is the major mineral in pozzolana materials. The silica in amorphous phase is known to be more reactive than in crystalline form (Siddique Rafat and Khan Mohammed Iqbal. 2011). Quartz, Cristobalite, and Glass are all different phases of Silica. Amorphous materials like glass, do not produce sharp diffraction peaks (Cullity, 1977). As shown in the Figure 3.6, the X-Ray is scattered in many directions leading a large bump distributed in a wide range (02 Theta) instead of high intensity narrower peaks.
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Figure 3.5 X-Ray Diffraction Result of Local Bagasse Ash The percentage of compounds are quantified using match software (See figure 3.5). However, the results are not necessarily compatible with complete silica analysis and requires XRD professionals for a more accurate analysis.
Complete Silica Analysis: The chemical property of bagasse ash and cement had been examined at Ethiopian Geological and Survey. The experiment result is reported in Table 3.6.
Table 3.6 Chemical Property of Cement and Bagasse Ash Compounds Bagasse Ash (%) Cement (%) SiO2 68.6 26.62
Al2O3 9.04 6.08 Fe2O3 5.24 4.82 CaO 1.52 55.30 MgO 1.36 1.1
Na2O 1.84 0.2 K2O 2.44 0.16 MnO 0.12 0.01
P2O5 0.51 0.08
TiO2 0.13 0.24 H2O 1.8 0.51 LOI 7.91 < 10 3.43 SiO2+ Al2O3+Fe2O3 83.18 > 75 -
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
The local bagasse ash satisfies the criteria specified in ASTM-C 618-00 (standard specification for coal fly ash and raw or calcined natural pozzolana for use as a mineral admixture in concrete). This local pozzolana possesses higher silica content and it can be characterized under Class-F pozzolana materials: indeed, it would insure secondary hydration activity.
3.1.4 Water Mixing water must not contain substances that cause degradation in quality like strength development, loss of workability, or steel corrosion in harmful quantities. The water used is from AAiT water supply pipe. Odor, Color, unusual tests were checked.
3.2 METHODS
The methods applied in order to achieve the objectives are elaborated in this section. It includes mixture design, test setups for both mechanical property and thermal experimental programs.
3.2.1 Mixture Design The mixture design is accomplished using ACI 211.1-91 standard procedure. Specified compressive strength of 25 MPa. (Required average compressive strength, 33 MPa.) was pre-assigned for the control group. The quantity of each ingredient for the control group is summarized in Table 3.7.
Table 3.7 Quantity of Material Required Per Metric Cube of Concrete No. Material Weight of material (kg/m3)
1 Water 190
2 Cement 334.51
3 Coarse aggregate 1046.52
`4 Fine aggregate 763.03
Using the above mixture proportion, a trial strength check had been carried out and confirmed the prescribed strength. In case of partial replacement of cement using bagasse ash, volume-based replacement method was adopted. Volume based replacement is
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures preferred in order to produce equal paste volume, that ensures justified comparison within all mixes. According to ACI 211.1-91 while using pozzolana material, Equation 3.1 can be used for determining the weight of pozzolana material as a function of the volume of replacement. 1 Fw ...... [Eq 3.1] 1 1 3.15 /Gp -1 Fv
Where: Fw = Weight of pozzolana
Gp = Specific gravity of pozzolana
Fv = Percentage volume replacement level
Table 3.8 Quantity of Bagasse Ash for Each Replacement Level Mixture Replacement Weight of Weight of Water/Binder Water/Binder (Adjusted) Id. Level (%) Bagasse ash Cement (Adjusted) By Weight By Volume (kg/m3) (kg/m3)
BA-0 0 0 334.5 0.568 0.559
BA-6.5 6.5 15.08 312.76 0.579 0.560
BA-13 13 30.82 291.02 0.591 0.562
BA-20 20 48.36 267.6 0.601 0.566
Where: - BA-0 = Control group with 100% OPC BA-6.5 = Mixture with 6.5 % of bagasse ash and 93.5% OPC BA-13 = Mixture with 13 % of bagasse ash and 87% OPC BA- 20 = Mixture with 20 % of bagasse ash and 80% OPC Since the weight of total binder decrease as an increase in bagasse ash replacement level, the water to binder ratio (in weight basis) will increase in some extent as shown in Table 3.8.
3.2.2 Mixing, Vibrating, and Curing Condition Pemat mixer has been used for mixing as specified in ASTM C-192. After all ingredients were mixed for 3 min; it was left to rest for 3 min followed by 2 min final mixing. Mixing
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures machine was lubricated with water in order to prevent it from absorbing mixing water. The slump of each freshly mixed concrete is measured according to ASTM C-143.
Figure 3.6 Measuring Slump of Fresh Concrete Placing of concrete into the mold is done according to ASTM C-192 specification using scoop, and shovel. The molds were half filled, vibrated, and then filled to top level before they vibrated again. In order to ensure a proper consolidation external vibrator is used. After the molds were fully filled, it has been kept in a rigid surface that is free from any vibration and disturbance. The specimens were removed from the mold at a time of 24 ± 8 hours, and has been kept in water container for providing a consistent curing condition. The specimens were removed from the water tank and placed at room temperature prior to testing.
Figure 3.7 (a) Mixing Machine (b) Curing Condition
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
3.2.3 Test Setup and Procedure
3.2.3.1 Mechanical properties Advanced testing methods combined with accurate analysis techniques is required for solid understanding of material property of young concrete. ASTM manual is adopted for clarifying the test setups and procedures.
Compressive Strength: Provides a general indication of concrete quality. Compressive strength was determined using 15*15*15cm3 cubical concrete cores at the laboratory. This test method consists of applying a compressive axial load at loading rate from 0.15- 0.3Mpa/sec to specimen until failure occurs (ASTM C-39). The compressive strength of the specimen can be calculated by dividing the load attained during the test by the cross- sectional area of the specimen. The universal compression testing machine used in this study is capable of determining both the failure load and stress.
Figure 3.8 Compressive Strength Test Setup
Tensile Strength: Tensile strength of concrete can be conducted using direct uniaxial and indirect methods such as flexural and splitting strength experiments. The direct tensile strength test is a good approach for determining concrete uniaxial tensile capacity. The drawback of this method is that, precise test set up is needed in order to avoid uncertainties.
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Splitting tensile strength test was used for this research. This method consists of applying a diametric compressive force along the length of a cylindrical concrete specimen at a rate of 689 to 1380 KPa/min until failure occurs (ASTM C-496-71). The state of stress in the plane of loading is uniform tension perpendicular to this plane (Timoshenko & Goodier 1970). The tensile stress is written in Equation 3.1 (ASTM C-496-71).
2*P ...... (3.1) DL Where : P = Applied load at failure D= Diameter of cylinder L= Length of cylinder
Flexural Strength: A third-point load experiment has been adopted for determining the flexural capacity as specified in ASTM C 78–00.
Figure 3.9 Flexural Strength Test Setup
The flexural strength of concrete using third-point load test can be calculated using Equation 3.2 (ASTM C 78–00). FL ...... (3.2) WD2 Where: F= Failure load L= Length of specimen W= Width of specimen D= Avarage depth of specimen
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3.2.3.2 Thermal Property The heat of hydration has been determined by a semi-adiabatic temperature rise experiment. The semi adiabatic temperature rise experiment is carried out because it had a similar property with adiabatic temperature rise owing small loss of heat with time. Therefore, the heat compensation method for estimating the adiabatic temperature rise using semi adiabatic tests is required. The heat compensation method can be implemented by considering flat curve at the point where temperature rise is maximum.
Molds made from plywood with a dimension of 30cm width, 30cm length and 40cm height are used for pouring the concrete in. The plywood is insulated using 10cm thickness Styrofoam to prevent the heat from escaping.
Figure 3.10 (a) Insulated Plywood Mold (b) Location of Sensors Throughout Depth
The upper part of the concrete mold is left open to simulate effect of ambient temperature. The temperature sensor has been embedded in the concrete at three places, top, center and bottom part as shown in Figure 3.11. Temperature is measured for each 30-minutes interval using thermocouples until the maximum heat is perceived. The temperature reading took six days, including night sessions. For three different ambient temperatures and four different replacement ratios, twelve specimens were cast.
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
Figure 3.11 Demolding and Demolishing Concrete Samples for Reusing Thermocouples
3.2.3.3 Temperature Chamber In order to simulate the effect of ambient temperature on the heat evolution of the concrete specimens which contain different dosages of bagasse ash, temperature chamber is constructed in the AAiT material laboratory. It was capable of simulating 250, 350, 450 C ambient temperatures.
Layout: The chamber has an internal dimension of 1.2m width, 3m length and 1.28m height. As shown in Figure 3.12, the Chamber was constructed from bricks. The door which serve as an entrance for the specimens is made-up of plywood and insulated by Styrofoam. The chamber is capable of accommodating three concrete samples at a time.
Figure 3.12 Chamber on Progress of Construction
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Controlling System: In order to control the room temperature (chamber temperature), computer algorism is developed with the help of Arduino software. LM-35 temperature sensor is used to read the chamber’s temperature; so that it will feed continues data to the monitoring device. After the Arduino received the data sent from the temperature sensor, it will translate information and command the relay attached at heaters. The heaters increase and decrease (on and off) the temperature, to produce constant internal ambient temperature.
Figure 3.13 Final Setup of Temperature Chamber with its Full Controlling System
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CHAPTER 4 RESULT AND DISCUSSION
This chapter discusses the result obtained as outlined in chapter three. The outcomes gained from the experimental program presented into two major parts: The first section addresses the mechanical strength development of concrete followed by the thermal investigations.
4.1 FRESH CONCRETE PROPERTIES
Optimization of pozzolana in concrete mixture might affect the fresh property of concrete. The average slump value for each replacement level is reported in Table 4.1.
Table 4.1 Average Slump Value for Each Mixture
Average Replacement Mixture Id. Water/Binder Slump Value Level (%) (mm)
BA-0 0 0.567 52
BA-6.5 6.5 0.579 38
BA-13 13 0.591 29
BA-20 20 0.601 17
As indicated in Table 4.1, loss of workability was detected with an increment in level of replacement. The physical and chemical features of bagasse ash could be the cause for this situation. Furthermore, the bagasse ash used in this study have 7.89% of loss of ignition that should be taken in to account for the phenomena.
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4.2 HARDENED CONCRETE PROPERTIES
4.2.1 Compressive Strength To study the early age compressive strength development of concrete, experiments have been carried out at one, two, three, seven and twenty-eight days for 0%, 6.5%, 13% and 20% cement-bagasse ash replacement levels. For each mixture, three specimens were tested and the average results are reported in Table 4.2.
Table 4.2 Average Compressive Strength
Average Compressive Strength (Mpa.) Mixture Id. Day-1 Day-2 Day-3 Day-7 Day-28
BA-0 8.49 11.9 16.14 23.92 29.19 BA-6.5 8.35 11.26 16.06 23.77 30.20 BA-13 7.7 10.54 15.13 23.38 31.13 BA-20 10.01 11.69 14.39 20.34 28.49 Remark: an additional paste volume has been introduced on mixture “BA-20” for insuring workability so that it is voided from the comparison between mixtures.
Although reduction in early age compressive strength development was observed, the cement-bagasse ash blends of 6.5 % and 13% replacement level satisfied the strength requirement at late age of testing (See Table 4.2). Higher strength was obtained on concrete specimens containing bagasse ash compared to pure cement concrete (control group).
The pozzolana reaction depends on hydration of cement particles. Bagasse ash is an inert material until it gets base solution from hydration of cement. Therefore, the reason for a drop in compressive strength at early age is that, enough calcium hydroxide (base solution) could not be available for the nonce. As the cement hydration continues, concentration of calcium hydroxide will be critical; Consequently, pozzolanic reaction initiates. Thus, it would not be surprising that pozzolana reaction magnifies at latter ages.
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Compressive Strength Development 35 30 25 20 15 10 5
Compressive (Mpa) Strength Compressive 0 1 2 3 7 28 Age (Days) BA-0 BA-6.5 BA-13 BA-20
Figure 4.1 Average Compressive Strength Development
The strength gains over time not only resulted due to reaction between pozzolana material and calcium hydroxide but also from the contribution of bagasse ash in facilitating the ordinary hydration process. Neville A.M (2011) states, after cement complexes (E.g. C3S) reacts with water, calcium hydroxide (byproduct of hydration) will act as a thin film around the remaining cement compounds like C2S; meanwhile, it will alter left over chemical reactions. The introduced bagasse ash absorbs calcium hydroxide solution from hydration products; Therefore, it will facilitate the ordinary hydration process and ensures ultimate strength development.
As shown in Figure 4.1, early age strength development of concrete containing 20% of sugarcane bagasse ash exceeds other mixtures. Since the first mix was harsh for cast, an additional paste volume was introduced in the concrete mix for ensuring workability. The cement paste added by controlling the water to binder ratio disrupted the early age mechanical property of concrete contains 20% bagasse ash. Full compressive strength result is documented in Appendix A, Table A.1.
4.2.2 Splitting Tensile Strength The tensile strength is the key property of concrete directly interrelated with early age cracking. Although premature failure considered as drawback of splitting tensile experiment, it has not been noticed throughout this study.
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Figure 4.2 (a) Test Set up of Splitting Tensile Strength Test (b) Test Specimen after Failure
The splitting strength testes have been conducted at one, two, three, seven and twenty- eight days. The average splitting tensile strength results are shown in Table 4.3.
Table 4.3 Average Splitting Tensile Strength of Concrete
Mixture Id. Average Splitting Tensile Strength (Mpa) Day-1 Day-2 Day-3 Day-7 Day-28 BA-0 0.76 1.55 1.86 2.14 2.69 BA-6.5 0.69 1.17 1.73 2.03 2.87 BA-13 0.57 0.88 1.44 1.97 2.92 BA-20 0.41 0.8 1.31 1.55 2.38
Figure 4.3 shows that, the tensile strength also enhances with time. Looking at late age strength development, pozzolanic reactivity induced by replacing cement using 6.5% and 13% of bagasse ash has ensured the desired strength (Control group).
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Splitting Tensile Strength Development 5.00
4.00
3.00
2.00 Tensile Strength (Mpa) Strength Tensile 1.00
0.00 Splitting 1 2 3 7 28 Age (Days) BA-0 BA-6.5 BA-13 BA-20
Figure 4.3 Splitting Tensile Strength Development
According to Mehta and Monterio (2006), micro cracking originates in the interfacial transition zone (ITZ) and cracking develops as load is applied. Empty voids could be formed in ITZ while water escapes from large aggregate surface in a form of bleeding. The progress of hydration (C-S-H formation) will eventually fill those empty voids and densify the ITZ. Optimizing bagasse ash in concrete mixture up to 13% replacement level further enhances tensile strength in a way, an additional C-S-H and ettringite will be induced from pozzolanic reaction. Substitution of weak calcium hydroxide layer found in ITZ by a more densified ettringite indeed increases the tensile capacity.
Remarkable early age tensile strength drop is observed on concrete samples containing bagasse ash (See Figure 4.3). According to chemical characterization, the local bagasse ash takes Class-F fly ash property. This pozzolana depends on hydration of cement and do not possesses self-hardening behavior; therefore, it could be major reason for reduction in early age splitting strength.
4.2.3 Flexural Strength As shown in Table 4.4, flexural strength of concrete contains 6.5% and 13% bagasse ash shows relatively higher value than the control group in late age of testing. On the other
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures hand, replacing of cement by bagasse ash up to 20% reduces both the early and late age flexural strength development of concrete.
Table 4.4 Average Flexural Strength Average Flexural Strength (Mpa) Mixture Id. 1 Day 2 Days 3 Days 7 Days 28 Days
BA-0 0.6 1.45 1.68 2.78 4.7
BA-6.5 0.65 1.33 1.58 2.9 5.0
BA-13 0.45 1.25 1.46 2.9 5.55
BA-20 0.38 1 1.35 2.3 3.95
Flexural Strength Development 5
4
3
2
1 Flexural (Mpa) Strength Flexural 0 1 2 3 7 28 Age (Days) BA-0 BA-6.5 BA-13 BA-20
Figure 4.4 Flexural Strength Development Portlandite (Calcium hydroxide) constitute 20 to 25 percent of the volume of solids in the hydrated paste. The strength-contributing potential of Portlandite is limited as a result of considerably lower surface area (Mehta and Monterio, 2006). The bagasse ash present in the hydrated paste undergoes a chemical reaction with Portlandite to create additional C- S-H and needle-shaped prismatic crystals (ettringite). Both as inert filler and pozzolanic reactivity, bagasse ash in concrete enhanced the quality of cement paste and the micro structure of the transition zone between the binder matrix and the aggregate. (See Table 4.4).
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4.3 EARLY AGE THERMAL PROPERTIES
The effect of ambient temperature on hydration heat of concrete containing bagasse ash is studied using temperature chamber. The internal heat evolution of concrete specimens was examined under 25.15º, 35.54º and 43.77º C average ambient temperatures. The ambient temperatures history is shown from Figure 4.5-4.7.
Figure 4.5 25.15º C Average Ambient Temperature History
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Figure 4.6 35.54º C Average Ambient Temperature History
Figure 4.7 43.77º C Average Ambient Temperature History
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4.3.1 Effect of Ambient Temperature on Heat Evolution The peak temperature gauges, for each replacement level under different ambient conditions and corresponding time of measurements are summarized in Table 4.5.
Table 4.5 Peak Temperature in Concrete Specimens Ambient Temperature 25.150C 35.640C 43.770C Mixture Position Hour Temp. Hour Temp. Hour Temp. Code (0C) (0C) (0C)
BA-0 Top 17 36.9 14.5 38.2 17.5 47.5 Middle 16.5 41.2 15.5 43.7 18.5 48.9 Bottom 16.5 43.9 16.5 47 19 51.4 BA-6.5 Top 17.5 35.5 15.5 37.3 19 45.5 Middle 16.5 38.5 17 42.2 21 46.1 Bottom 16 41.3 18 45.3 22 48.7 BA-13 Top 18 33.8 16 36.7 20 43.5 Middle 17.5 36.4 16.5 40.2 21.5 44.8 Bottom 18 39.3 18.5 42.7 23 46.4 BA-20 Top 20 32.3 17 35.2 16.5 39.9 Middle 19.5 35 18.5 38.9 18.5 40.8 Bottom 19 37.3 20 41.4 19 43
As pre stated by ACI 207(1995), the semi adiabatic temperature rise experiments outcome of this study clearly shows that, the hydration heat liberation of concrete specimens escalates as the ambient temperature increase. The temperature rise-time curve, magnitude of maximum temperature gauge, early age reaction rate, thermal gradient, cooling rate of concrete are all under the influence of ambient condition. The temperature profile through different ambient temperatures for each concrete mixture is shown from Figure 4.8-4.19.
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BA-0 Temperature Profile 50 45
40 C C ) ° 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour
BA-0 T BA-0 M BA-0 B Amb. Temp.
Figure 4.8 Temperature Profile of Control Specimen at 25.150 Ambient Temperature
BA-0 Temperature Profile
55 50
45 C C )
° 40 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-0 T BA-0 M BA-0 B Amb. Temp
Figure 4.9 Temperature Profile of Control Specimen at 35.540 Ambient Temperature
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BA-0 Temperature Profile 55 50
C C ) 45 ° 40 35 30 25 20
Temperature ( Temperature 15 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-0 T BA-0 M BA-0 B Amb. Temp
Figure 4.10 Temperature Profile of Control Specimen at 43.770 Ambient Temperature
BA-6.5 Temperature Profile 45 40
35 C C )
° 30 25 20 15 10
Temperature ( Temperature 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-6.5 T BA-6.5 M BA-6.5 B Amb. Temp.
Figure 4.11 Temperature Profile of Concrete Specimen Contain 6.5% BA at 25.150 Ambient Temperature
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BA-6.5 Temperature Profile 50 45 40
C C ) 35 ° 30 25 20 15
10 Temperature ( Temperature 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-6.5 T BA-6.5 M BA-6.5 B Amb. Temp
Figure 4.12 Temperature Profile of Concrete Specimen Contain 6.5% BA at 35.540 Ambient Temperature
BA-6.5 Temperature Profile 55 50
45 C C )
° 40 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-6.5 T BA-6.5 M BA-6.5 B Amb. Temp
Figure 4.13 Temperature Profile of Concrete Specimen Contain 6.5% BA at 43.770 Ambient Temperature
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BA-13 Temperature Profile 45 40
C C ) 35 ° 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-13 T BA-13 M BA-13 B Amb. Temp.
Figure 4.14 Temperature Profile of Concrete Specimen Contain BA 13% BA at 25.150 Ambient Temperature
BA-13 Temperature Profile 50 45
C C ) 40 ° 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-13 T BA-13 M BA-13 B Amb. Temp
Figure 4.15 Temperature Profile of Concrete Specimen Contain 13% BA at 35.540 Ambient Temperature
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BA-13 Temprature Profile 50 45
C C ) 40 ° 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-13 T BA-13 M BA-13 B Amb. Temp
Figure 4.16 Temperature Profile of Concrete Specimen Contain 13% BA at 43.770 Ambient Temperature
BA-20 Temperature Profile 50 45
40 C C )
° 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hours BA-20 T BA-20 M BA-20 B Amb. Temp.
Figure 4.17 Temperature Profile of Concrete Specimen Contain 20% BA at 25.150 Ambient Temperature
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BA-20 Temperature Profile 50 45 40
C C ) 35 ° 30 25 20 15
10 Temperature ( Temperature 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-20 T BA-20 M BA-20 B Amb. Temp
Figure 4.18 Temperature Profile of Concrete Specimen Contain 20% BA at 35.540 Ambient Temperature
BA-20 Temperature Profile
50 45
40 C C ) ° 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-20 T BA-20 M BA-20 B Amb. Temp
Figure 4.19 Temperature Profile of Concrete Specimen Contain 20% BA at 45.770 Ambient Temperature
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Figures 4.8-4.10 show the temperature profile of cement concrete at 25.25º, 35.54º and 43.77º C. The peak temperature was gauged at the bottom part of specimen since insulation have been provided at surface of concrete in all direction except the upper part, which was left open intentionally. The insulation (Styrofoam) allows the interior concrete to reach a higher temperature by slowing the diffusion of heat generated from the hydration of cement and chamber temperature radiation. The covering also insulates the concrete surface from the ambient temperature cycles which decreases the temperature drop between the mid-depth and the covered surface.
The peak temperature induced at bottom part of control specimen increased by 17% as the ambient temperature changed from 25.150 to 43.770 C. In addition, the time required to reach peak temperature of 43.90 C was decreased from 16.5 hours to 12.5 hours. In case of concrete containing 6.5%, 13% and 20% dosages of bagasse ash, the ultimate temperature was decreased but the heat evolution corresponding to ambient temperature was significantly influenced.
According to Siddique and Mohammed (2011), pozzolana reaction is slow, releasing heat over a long period of time and not taking place at a very early age of hydration. Similarly, in this study, the effect of bagasse ash on the pattern of hydration heat is pronounced. Temperature profile spectacles, the first 4-6 hour of hydration was slow for all mixes at 25.150 C ambient temperature. The control group reaction starts to accelerate even for the first 2-3 hours as the ambient temperature increases. On contrast, mixture contain 13% and 20% of bagasse ash heat liberation rate is relatively slower even in higher ambient temperature (See Figures 4.8 - 4.19).
The maximum temperature differential generally occurred when the maximum internal temperature occurred. The concrete specimens monitored show that, the temperature gradient is trivial over the middle portion of the member and relatively steep towards the surface. Thus it is clear that the temperature drop within a concrete specimen from bottom depth to the exposed surface is not linear, but rather most of the temperature drop occurs near the exposed concrete surface. As a result, current guideline using a linear distribution for estimation of thermal stress developed due to internal heat of hydration comes in to question.
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Thermal gradient within section of specimen was decreased by more than 52% for all mixtures after the ambient vary from 25.150 to 43.770 C. At higher ambient temperature, diffusion of heat from top surface of concrete to the surrounding medium is insignificant. Beside higher ambient transfers heat to the surface of concrete specimen such that, the thermal gradient between top and bottom surface remains low. On the other hand, the thermal gradient increased up to 38% as the ambient changed from 25.150 to 35.530 C. This phenomenon was surprising but it had a logical background. Relatively intermediate ambient temperature may not have significant effect in heating the top surface of specimen, rather it will facilitate the internal rate of hydration and increase the core temperature concurrently resulting an increment in thermal gradient.
According to ACI 207 (1995), the temperature difference between the ambient temperature and concrete structure should be less than 200 C in order to avoid thermal shock. The temperature difference between the cement concrete and ambient (25.150) was 18.750 C; slightly less than the value specified by ACI 207. Under ambient temperatures of 35.540 and 43.770 C, the thermal gradients are 11.460 and 7.630 C respectively; less risky than the former.
Although cold area concreting has favorable effect in mitigating cracking risk (Since the rate of hydration will decrease), it could create potential problems too. In cold ambient temperature, massive concrete structures undergo rapid loss of heat to surrounding medium, which is a reason for thermal gradient and thermal shocks (See Figures 4.8, 4.11, 4.14, 4.17). Thus, emphasis should have to be given for mass concrete placements in cold areas.
4.3.2 The Effect of Bagasse Ash on Early Age Heat Evolution In previous section, the effect of ambient temperature on rate of reaction and heat liberation of concrete specimens containing pure cement and different dosages of bagasse ash was discussed. This session will particularly discuss the effect of bagasse ash on the heat evolution of concrete mixtures. The Figures 4.20-4.28 show the semi-adiabatic temperature data of different concrete mixtures.
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Top Temperature Profile 50 45
C C ) 40 ° 35 30 25 20 15 Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-0 T BA-6.5 T BA-13 T BA-20 T Amb. Temp.
Figure 4.20 Top Temperature Profile of Different Mixture Specimens at 25.150 Ambient Temperature
Middle Temperature Profile 50 45
40 C C ) ° 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-0 M BA-6.5 M BA-13 M BA-20 M Amb. Temp.
Figure 4.21 Middle Temperature Profile of Different Mixture Specimens at 25.150 Ambient Temperature
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Bottom Temperature Profile 50 45
40 C C ) ° 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-0 B BA-6.5 B BA-13 B BA-20 B Amb. Temp.
Figure 4.22 Bottom Temperature Profile of Different Mixture Specimens at 25.150 Ambient Temperature
Top Temperature Profile 50 45
40 C C )
° 35 30 25 20
15 Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-0 T BA-6.5 T BA-13 T BA-20 T Amb. Temp
Figure 4.23 Top Temperature Profile of Different Mixture Specimens at 35.540 Ambient Temperature
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Middle Temperature Profile 50 45
40 C C ) ° 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-0 M BA-6.5 M BA-13 M BA-20 M Amb. Temp
Figure 4.24 Middle Temperature Profile of Different Mixture Specimens at 35.540 Ambient Temperature
Bottom Temperature Profile 50 45 40
C C ) 35 ° 30 25 20 15 10
Temperature ( Temperature 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26
Hour BA-0 B BA-6.5 B BA-13 B BA-20 B Amb. Temp
Figure 4.25 Bottom Temperature Profile of Different Mixture Specimens at 35.540 Ambient Temperature
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Top Temperature Profile 55
50
45 40 35 30 25
20
Temperature (°C) Temperature 15 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-0 T BA-6.5 T BA-13 T BA-20 T Amb. Temp
Figure 4.26 Top Temperature Profile of Different Mixture Specimens at 43.770 Ambient Temperature
Middle Temperature Profile
55 50
45 C C )
° 40 35 30 25 20 15
Temperature ( Temperature 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-0 M BA-6.5 M BA-13 M BA-20 M Amb. Temp
Figure 4.27 Middle Temperature Profile of Different Mixture Specimens at 43.770 Ambient Temperature
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Bottom Temperature Profile 55 50
C C ) 45 ° 40 35 30 25 20
Temperature ( Temperature 15 10 5 0 0.5 3.5 6.5 9.5 12.5 15.5 18.5 21.5 26 Hour BA-0 B BA-6.5 B BA-13 B BA-20 B Amb. Temp
Figure 4.28 Bottom Temperature Profile of Different Mixture Specimens at 43.770 Ambient Temperature
The presence of bagasse ash in concrete mixture has dropped the total heat liberated from concrete specimens. The decline in temperature is detected throughout the depth of all concrete specimens containing bagasse ash. Replacing 20% of cement using bagasse ash can drop the peak temperature of cement concrete specimens by 15%, 11.9% and 16.3% for 25.150, 35.540 and 43.770 C ambient condition respectively. This is of immense advantage in massive concrete placement where cooling, following a large temperature rise, can lead to cracking. Likewise, using bagasse ash in 6.5% and 13% replacement level reduce the overall temperature rise of the concrete depending on ambient conditions, however the effect is less due to lower replacement level.
The decrease in temperature appears to be due to the inertness of the bagasse ash at early age. On the other hand, low calcium pozzolana (Local bagasse ash) does not possess self- cementitious property; Therefore, it will not react rapidly with water and release excessive heat just like ordinary Portland cement. Furthermore, bagasse ash bind calcium ions effectively (calcium complexation) without releasing it for desired amount of time, so the hydration is delayed and early age heat evolution is retarded.
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Optimization of bagasse ash in concrete shows remarkable shift in temperature rise-time curve. Replacing 13% of cement using bagasse ash elongates the time required to reach 390 C internal temperature of specimen by 6, 3.5, and 3 hours under 25.150, 35.540 and 43.770 C ambient temperature respectively. Shifting the temperature rise-time curve by elongating the time required to attain peak magnitude have an optimistic impact in a way, concrete gets additional time for strength development before the thermal load exerted.
Moreover, reduction of thermal gradient is observed as the cement-bagasse replacement level increases. In the case of 13% replacement level, the thermal gradient of cement concrete was decreased by 21.4%, 31.81% and 25.64% for 25.150, 35.540 and 43.770 C ambient temperature respectively.
As shown in the Figures 4.21-4.25, the temperature profile of each concrete mixture do not commence at similar temperature gauge. Since the concrete mixtures were not cast all together, there was a variation of initial temperature until the specimens placed in the chamber. Thus, concrete mixtures casted at lower ambient temperature will eventually show a relatively slow reaction rate compared with the high initial casting temperature. The initial concrete temperature affects the rate of heat liberation which is essential for concrete in a semi-adiabatic environment (moderate mass concrete placements). Pre- cooling of concrete is among the “initial temperature reduction techniques”, which can be used to reduce the internal temperature rise by decreasing the rate of heat generation. The lower rate of heat liberation provides a longer time for heat to dissipate which decreases the potential for thermal cracking due to a thermal gradient within a concrete structure.
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CHAPTER 5 FINITE ELEMENT MODELING
In recent years, with advancement in computing technology, significant progress in finite element approach tools have been observed. Finite element analysis based confirmation tools (softwares packages) are helpful in identifying obstacles at early stage of design, reducesing prototyping cost, gaining perceptions on phenomenon which cannot be easily dignified in physical tests, etc. Hacon-3 finite element sofware is used to simulate hardining concrete under different ambient tempretures. The input parameters, modeling issues and finally results are discussed here after.
5.1 MODEL DESCRIPTION
Finite element modeling is used for validating the result obtained from experimental programs. Concrete samples used in experimental programs were modeled with corresponding dimensions, physical properties and different boundary condition including ambient temperature. Moreover, investigation of thermal crack risk, and parametric study was undertaken using this finite element software.
5.2 ABOUT HACON-3 FES
Hacon-3 finite element software was developed for simulation of temperature and stress in hardening concrete structures. The software is open source and can handle a two dimensional and axisymmetric problems. Modeling the stage of construction, introducing ambient temperature, modeling insulation and formworks, creating cement parameters are important features of this software. Additionally, modeling of creep, stress induced thermal strain, autogenous shrinkage and development of crack can be studied using this FES.
5.3 INPUT PARAMETERS
The Input data for numerical study are according to previously done experiments and relevant mathematical formulation/relation proposed in literatures.
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5.3.1 Specific Heat Capacity Specific heat capacity is the amount of heat needed to change the temperature of 1g of material by 1°C (Lawrence, 2016). A typical value of specific heat capacity for concrete ranges from 0.92–1.00 kJ/kg°C according to ACI 207 and 840 to 1170 J/kg°C as per Neville (2011). For this study 840 J/kg°C was adopted.
5.3.2 Thermal Conductivity Thermal conductivity is a thermo-physical measure of how much heat can be transferred through a material of conductive flow (Neville, 2011). The thermal conductivity of concrete is affected by various parameters including the type of aggregate, moisture content, porosity of the concrete and degree of hydration. According to ACI-207, the thermal conductivity of concrete is in the range of 7.1 to 10.6 kJ/mh°C. In this study thermal conductivity; 8 kJ/mh°C is taken.
5.3.3 Coefficient of Thermal Expansion Coefficient of thermal expansion describes how the size of an element changes due to a change of temperature. According to Meyers (1951), The linear coefficient of thermal expansion of hydrated cement paste varies between 11 × l0–6 and 20 × 10–6/°C. The coefficient of thermal expansion used in this study is 10*10-6 per °C.
5.3.4 Thermal Diffusivity Thermal diffusivity is a measure of easiness or difficulty of concrete undergoing temperature change (ACI 207, 1995). The range of typical values of diffusivity of ordinary concrete is between 0.002 and 0.006m2/h (Neville, 2011). An average value of 0.004 m2/h is specified for modeling.
5.3.5 Total Heat of Hydration Degree of hydration of concrete is the foremost important parameter for simulating the early age thermal behavior of a structure (Lawrence, 2009). For common cement types, the hydration is exothermic reaction and up to 500J/g (120 cal/g) energy can be liberated (Neville, 2011). Heat of hydration is not the same for all mixtures. It depends on the chemical compositions of cement, proportion of each compositions and addition of supplementary materials. The hydration heat can be expressed mathematically using Equation 5.1 & 5.2 (Schindler and Folliard, 2005).
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Hcem =500C 3 S 260 C 2 S 866 C 3 A 420 C 4 AF 624 S 0 3 1186 freeCao 850 Mgo ...... (5.1) Where:- = is thepercentage fraction of thei th compounds in the cement
To account the heat of hydration from supplementary cementitious materials, the equation can be further modified as
Hucement* H cement flyash * H flyash ...... (5.2) where: Hflyash =1800 cao j / g or 209 j / g = percentageof fly ash
However, heat of hydration for total amount of cement is affected by the chemical compositions interaction. The heat of hydration is given by Equation 5.3 (Neville, 2011).
136(C3S) + 62(C2S) + 200(C3A) +30(C4AF) ……………………………...……...(5.3)
The specific heat of hydration for cement with different cement-bagasse ash replacement ratio is computed as per Equation 5.1, 5.2 & 5.3 and summarized in Table 5.1.
Table 5.1 Ultimate Heat of Hydration for Different Mixtures Mixture Id. Ultimate heat of hydration(j/g) BA-0 220.63 BA-6.5 208.04 BA-13 192.29 BA-20 177.44
All the specified input parameters may not represent concrete specimens containing bagasse ash; However, a relatively convenient value is specified for the finite element modeling.
5.4 MODELING
5.4.1 Geometry The first task in modeling is creating nodes. The nodes are then connected using lines or curve elements. Surface has been created by selecting the desired lines in counter clock wise direction. Hacon-3 provides an option for selecting 3, 5 or 8-noded elements. 8
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures nodded elements are used for this modeling. Meshing was done by specifying the desired amount of columns and rows in the finite element software.
Figure 5.1 Meshing and Element Property
5.4.2 Material In Hacon-3 there are some predefined materials such as concrete, rock and soil. K-40 concrete material is used, but the default material property was latter modified. In material session; placing temperature, cement content, water/binder, ultimate heat of hydration and time for initiation of maturity are all defined.
Figure 5.2 Material Modeling Tab in Hacon-3
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5.4.3 Boundary Conditions After all, the boundary conditions are the critical governing factor for simulating the thermal analysis later for staggered structural analysis. The base and sides of the concrete has been fixed in order to get worst case scenario. The concrete specimens were insulated in three directions (the top surface will remain exposed so that the effect of ambient temperature can be simulated). Hacon-3 provides different insulating materials; Moreover, other materials of different physical properties can be introduced. A 10 Cm thickness Styrofoam is modeled with its corresponding insulation property.
Figure 5.3 Assigned Boundary Conditions on Specimen Surface
5.4.4 Analysis Before the analysis began, Hacon-3 offers calculation setting in order to choose the desired time step, analysis type and output arrangement. The analysis was carried out for each 30- minutes time step; Therefore, the outcomes will be compatible with experimental program.
5.5 RESULT AND DISCUSSION
5.5.1 Hydration Heat Simulation Since the specimen was insulated in all directions except the upper part, the peak temperature of all concrete specimens simulated in Hacon-3 was located at the bottom part.
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Figure 5.4 Temperature Profile of the Control Group at 25.150 Ambient Temperature
Figure 5.4 shows that, peak temperature is 440 C and occurred 17 hours later after casting. The results from finite element analysis show a good agreement with the experimental outcomes in terms of predicting locations, magnitude and time delay of peak temperatures.
Bottom Temperature Profile 50
C C ) 40 °
30
20
Temperature ( Temperature 10
0 1 5 9 13 17 21 25 Hour Experiment Finite Element
Figure 5.5 Bottom Temperature Profile at Ambient Temperature 25.150 C
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Bottom Temperature Profile 60
50
C C ) ° 40
30
20
Temperature ( Temperature 10
0 1 5 9 13 17 21 25 Hour Experiment Finite Element
Figure 5.6 Bottom Temperature Profile at Ambient Temperature of 35.540 C
Bottom Temperature Profile 60
50 C C ) ° 40
30
20
Temperature ( Temperature 10
0 1 5 9 13 17 21 25 Hour Experiment Finite Element
Figure 5.7 Bottom Temperature Profile at Ambient Temperature of 43.770 C
It can be observed from Figure 5.5-5.7, thermal responses under different ambient temperature are well predicted using Hacon-3 finite element software.
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5.5.2 Cracking Risk Simulation Cracking start to initiate when the crack index is greater than 100%. Which means the stress induced by combined action of thermal and structural loads exceeds the strength of concrete.
The thermal cracking risk for the first 24 hours is trivial for all scenarios. As temperature increases the concrete attempts to expand, indeed the specimen will be under compression at the time of heat evolution. Usually the compressive strength of concrete is adequate to resist those minor compression forces. Moreover, the cracking risk plot is flatted for certain duration because specimen is under compression and tensile stress are almost zero. (See Figures 5.12-5.14).
Cracking Risk 70 60 50 40
30 Strength (%) Strength Ratio - 20
10 Stress 0 1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 Hour BA-0 BA-6.5 BA-13 BA-20
Figure 5.8 Cracking Risk at Ambient Temperature of 25.150
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Cracking Risk 50 45 40 35 30 25 20
Strength Strength Ratio(%) 15 - 10 5
Stress 0 1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 Hour BA-0 BA-6.5 BA-13 BA-20
Figure 5.9 Cracking Risk at Ambient Temperature of 35.540
Cracking Risk 40 35 30 25 20
15 Strength Strength Ratio(%) - 10
5 Stress 0 1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 Hour BA-0 BA-6.5 BA-13 BA-20
Figure 5.10 Cracking Risk at Ambient Temperature of 43.770 The tensile stress being minimal at the time of heat evolution does not mean that, the peak temperature will not influence thermal cracking, rather consequences get manifested on cooling stage of concrete. As it can be seen in the Figure 5.8-5.10, the cracking risk increase on the cooling phase as the tensile stress increases. Ambient temperature affects not only the heat liberation but also the cracking risk. The 72 hours cracking risk decrease up to 18.29%, 37.9% as the ambient varies from 25.150 to 35.540 and 43.770 C respectively.
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When the ambient temperature increases, the heat loss from the concrete decrease so that it will elongate the time for concrete contraction. Even though higher ambient temperature lowers the ultimate cracking risk by increasing the maturity of concrete and decreasing the tensile stress, it will increase the cracking risk at the very early age.
Introducing bagasse ash to a concrete mixture played a role in reducing thermal cracking risk. Thermal cracking risk after 72 hours is reduced by 17.68%, 32.83% and 29.34% after 6.5%, 13% and 20% of cement is replaced by bagasse ash respectively. Replacing cement up to 20% using bagasse ash clearly increased thermal risk in the first 16 hours for all ambient temperatures. Decreases in mechanical property of concrete containing 20% of bagasse ash is attributed to the phenomena. Although optimization of supplementary materials such as bagasse ash reduce the heat evolution, compatibility with strength requirement should be checked.
5.5.3 Influence of Insulation on Thermal Gradient As discussed in literature section, researchers recommend adoption of insulation in mass concrete structure for reducing thermal gradient. Different size concrete specimens were modeled with and without insulation. The outcomes were alarming.
Figure 5.11Temperature Profile of Insulated Concrete at 25.150 C Ambient Temperature (Size: 0.3m*0.4m)
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Figure 5.12 Temperature Profile of not Insulated Concrete at 25.150 C Ambient Temperature (Size: 0.3m*0.4m)
Figure 5.13 Temperature Profile of Insulated Concrete at 25.150 C Ambient Temperature (Size: 3m*4 m)
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Figure 5.14 Temperature Profile of not Insulated Concrete at 25.150 C Ambient Temperature (Size: 3m*4 m) As shown in Figures 5.11 & 5.12, for Specimen size: 0.3m*0.4m, the thermal gradient of insulated concrete is greater than non-insulated one. On contrast, when the size of specimen increases, providing insulation effectively reduces the thermal gradient as shown in Figures 5.13 & 5.14.
Thermal Gradient 35
30 C C )
° 25 20 15 10 Temperature ( Temperature 5 0 0 8 16 24 32 40 48 56 64 72 88 104 136 168 Hour Insulated; (3m*4m ) Not Insulated; (3m*4m) Insulated; (0.3m*0.4m) Not Insulated; (0.3m*0.4m)
Figure 5.15 Thermal Gradient of Insulated and Concrete without Insulation
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It can be seen in Figure 5.15 that; the rate of cooling is significantly decreased due to provision of insulation. Slow rate of cooling has positive impact in lowering thermal risk. Despite the merits, it cannot be thought that provision of insulation will decrease the thermal gradient for all cases. Thermal gradient is affected by so many factors such as; Insulation condition, size of concrete structures, material properties and environmental conditions. Therefore, before proposing insulation for mitigating thermal cracking risk in mass concrete structures, comprehensive analyses should be carried out for each specific projects.
5.5.4 Influence of Specimen Size on Thermal Gradient Concrete specimens with four different section dimension were modeled in Hacon-3. The thermal gradient-time curve is shown in Figure 5.16.
Thermal Gradient 40
35 C C ) ° 30 25 20 15
Temperature ( Temperature 10 5 0 0 8 16 24 32 40 48 56 64 72 88 104 136 168 Hour 0.3m*0.4m 1.5m*2m 3m*4m 12m*16m
Figure 5.16 Thermal Gradient of Different Size Concrete Specimens
As the size of concrete specimen increases, internal heat will rise, but the outer surface of concrete temperature converges to the ambient temperature. Thus, thermal gradient will increase for an increment in specimen size. The cooling rate and temperature rise are also factors influenced by size of concrete specimen.
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CHAPTER 6 CONCLUSION AND RECOMMENDATION
6.1 CONCLUSION
The main objective of this research was to understand early age thermal and mechanical properties of concrete contain bagasse ash under different ambient temperatures. The goal was achieved by undertaking experimental programs on concrete specimens encompassing different cement-bagasse ash proportions. Along the way, many significant conclusions were drawn and are stipulated below.
Optimization of bagasse ash in concrete should be inclusive of early age strength development. In the present study, the early age strength development of concrete containing bagasse ash was retarded; However, strength enhancement was observed at late age of testing. Ambient temperature significantly affects both cement concrete and concrete containing bagasse ash. Although reduction in peak temperature up to 16.3% is observed while replacing cement by bagasse ash, heat liberation of all mixtures increase as the ambient temperature rises. Concrete specimens of all mixtures experienced higher thermal gradient at lower ambient temperature; Therefore, cold area concrete placements should get proper attention. Incorporating bagasse ash in concrete reduced thermal gradient inside the specimens. Moreover, this pozzolana decreased the total heat of hydration and elongated the time required for the occurrence of peak temperature by retarding early age chemical reactions. Thermal cracking risk has been dropped while using bagasse ash as partial cement replacing material. However, using a higher dosage of bagasse ash could retard the strength development and consequently escalates the risk of cracking. Adapting insulation at surface of concrete structures is not always a wise choice for minimizing thermal gradients. Since thermal gradient depends on factor such as insulation, size of concrete structures, material properties and environmental conditions, comprehensive studies and design should be carried out for each specific projects.
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6.2 RECOMMENDATIONS FOR FUTURE WORK
While maintaining the favorable property in the retarding heat of hydration, other studies should be undertaken for enhancing the early age strength development of concrete containing bagasse ash. In this thesis, semi adiabatic temperature rise experiment was carried out, but this was not precise in predicting concrete temperature. Studies incorporating isothermal calorimetry and adiabatic temperature rise experiments should follow through.
In the present study, cracking risk is simulated using finite element software; However, Tensile Strength Testing Machine (TSTM) and Cracking Frame can be implemented for better investigations.
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APPENDIX A
MECHANICAL PROPERTIES DATA
Table A.1 Compressive Strength Experiment Data, 0% and 6.5% Replacement Level
Failure Failure Mixture Stress Avg. Mixture Stress Avg. Test Date Load Test Date Load Code (Mpa) (Mpa) Code (Mpa) (Mpa) (KN) (KN)
215.7 9.59 201.4 8.95 1 191.9 8.53 8.49 1 185.5 8.25 8.35 165.7 7.36 176.3 7.84 288.2 12.81 240.1 10.67 2 292.6 13.01 11.9 2 252.4 11.22 11.26 222.3 9.88 267.3 11.88 399.6 17.76 386.2 17.16 BA-0 BA-6.5 3 310.8 13.81 16.14 3 326.7 14.52 16.06 378.8 16.84 367.7 16.34 538.2 23.9 506.5 22.51 7 523.4 23.35 23.92 7 556.6 24.74 23.77 551.9 24.84 541.9 24.08 677.2 30.12 654.5 30.12 28 633.4 28.15 29.19 28 692.1 30.76 30.2 659.5 29.32 669.2 29.74
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Table A.2 Compressive Strength Experiment Data, 13% and 20 % Replacement Level
Failure Failure Mixture Stress Avg. Mixture Stress Avg Test Date Load Test Date Load Code (Mpa) (Mpa) Code (Mpa) (Mpa). (KN) (KN)
160.4 7.13 233.1 10.36 1 202.2 8.13 7.7 1 238.3 10.59 10.01 176.5 7.84 204.5 9.09 235.2 10.46 234.5 10.42 2 268.4 10.93 10.54 2 304.7 12.54 11.69 230.4 10.24 272.9 12.13 324.2 14.41 326.3 14.5 BA-13 BA-20 3 343.5 15.26 15.13 3 310.8 13.81 14.39 354 15.73 334.6 14.87 524.9 23.33 424.4 18.86 7 508.8 22.61 23.28 7 456.9 20.31 20.34 537.9 23.91 491.8 21.86 663.9 29.51 627.6 27.89 28 719.8 31.99 31.13 28 675.9 30.03 28.49 717.5 31.89 624.8 27.77
Table A.3 Flexural Strength Experiment Data, 0% and 6.5% Replacement Level
Failure Failure Mixture Stress Avg. Mixture Stress Avg. Test Date Load Test Date Load Code (Mpa) (Mpa) Code (Mpa) (Mpa) (KN) (KN)
1.2 0.6 1.4 0.7 1 0.6 1 0.7 1.2 0.6 1.4 0.7 3.1 1.55 2.8 1.4 2 1.45 2 1.33 2.7 1.35 2.5 1.25 3.3 1.65 3.2 1.6 BA-0 3 1.68 BA-6.5 3 1.58 3.4 1.7 3.1 1.55 6.2 3.1 5.9 2.95 7 2.95 7 2.9 5.6 2.8 5.7 2.85 10.2 5.1 10.2 5.1 28 4.7 28 5 8.6 4.3 9.8 4.9
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Table 4.4 Flexural Strength Experimental Data, 13 % and 20 % Replacement Level
Failure Failure Mixtue Stress Avg. Mixture Stress Avg. Test Date Load Test Date Load Code (Mpa) (Mpa) Code (Mpa) (Mpa) (KN) (KN)
1 0.5 0.7 0.35 1 0.45 1 0.38 0.8 0.4 0.8 0.4 2.4 1.2 2 1 2 1.25 2 1 2.6 1.3 2 1 2.8 1.4 2.8 1.4 BA-13 3 1.46 BA-20 3 1.35 3 1.5 2.6 1.3 6 3 4.3 2.15 7 2.9 7 2.3 5.6 2.8 4.9 2.45 10.8 5.4 8.3 4.15 28 5.55 28 3.95 11.4 5.7 7.5 3.75
Table A.5 Splitting Tensile Strength Experiment Data, 0% and 6.5% Replacement Level
Failure Failure Mixture Stress Avg. Mixture Stress Avg. Test Date Load Test Date Load Code (Mpa) (Mpa) Code (Mpa) (Mpa) (KN) (KN)
44.5 0.63 55.7 0.79 1 0.76 1 0.69 62.9 0.89 41.8 0.59 118 1.67 82.9 1.17 2 1.55 2 1.17 100.9 1.43 81.9 1.15 135.2 1.91 118.2 1.67 BA-0 3 1.86 BA-6.5 3 1.73 127.7 1.81 126.4 1.78 149.1 2.11 148.7 2.10 7 2.14 7 2.03 153.7 2.17 138.7 1.96 194.4 2.47 218.3 2.78 28 2.69 28 2.87 227.9 2.90 232.6 2.96
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Table A.6 Splitting Tensile Strength Experimental Data, 13 % and 20 % Replacement Level
Failure Failure Mixture Stress Avg. Mixture Stress Avg. Test Date Load Test Date Load Code (Mpa) (Mpa) Code (Mpa) (Mpa) (KN) (KN)
38.2 0.49 29.8 0.38 1 0.57 1 0.41 50.9 0.65 34.2 0.44 64.5 0.82 56.2 0.72 2 0.88 2 0.8 73.7 0.94 69.3 0.88 107.2 1.36 97.8 1.24 BA-13 3 1.44 BA-20 3 1.31 119.3 1.52 107.8 1.37 153.3 1.95 126.9 1.62 7 1.97 7 1.55 156.2 1.98 115.5 1.47 224.4 2.86 185.3 2.35 28 2.92 28 2.38 233.6 2.97 189 2.41
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APPENDIX B
SEMI ADIABATIC TEMPERATURE RISE
Table B.1 Semi Adiabatic Temperature Rise Data at Average Ambient Temperature of 25.150C
Mixture Code Amb. Hours BA-0 BA-6.5 BA-13 BA-20 Temp. T M B T M B T M B T M B 0.5 19.1 20.2 19.6 19.2 19.7 19.5 18.3 18.3 18.2 18.6 17.1 17.6 25.21 1 19.2 20.7 20.3 19.3 20.5 20.2 19 18.8 18.7 18.5 17.5 17.6 25.35 1.5 19.3 21.1 21.7 19.3 20.7 20.4 19.2 19 19.1 18.5 18.1 18.7 24.99 2 19.4 21.1 22.2 19.4 20.9 21.1 19.2 19.3 19.4 18.3 18.4 18.9 25 2.5 19.7 21.2 22 19.6 20.9 21.7 19.3 19.8 19.6 18.9 18.6 19 25.23 3 19.8 21.2 22 19.7 20.9 21.8 19.8 20.2 20.1 19.3 18.9 19.1 24.97 3.5 20 21.3 22 19.8 21 21.8 19.8 20.4 20.5 19.5 19.1 19.3 25.06 4 20.3 21.7 22.1 19.9 21.3 21.9 20.4 20.7 20.7 19.6 19.5 19.5 25.17 4.5 21.7 22.8 22.2 20 22.1 22.1 20.3 21.4 21.3 19.8 20.1 19.9 25.04 5 23.6 24.2 23.7 19.9 22.9 22.4 20.4 21.6 21.7 19.8 20.5 20 25.1 5.5 24.6 25.1 24.6 20.8 23.7 23.1 21.4 22.1 21.9 19.9 20.9 20.1 25.13 6 26.6 27.3 26.8 22.7 25.5 24.2 21.9 23 22.6 20.3 21.3 20.3 24.76 6.5 27.1 27.9 27.1 23.6 26.8 25 22.2 23.8 22.7 20.8 21.8 20.7 24.91 7 27.4 28.1 27.8 23.9 27.6 27 23.1 25.5 24.4 21.2 22.5 21.4 25.12 7.5 28.4 29.2 28.8 24.6 28.5 27.8 23.5 27 25.6 21.9 24.1 22.1 25.25 8 29.6 30.5 30.2 25.1 29.5 28.7 24.4 28 26.5 22.7 24.5 23.7 25.01 8.5 30.3 31.5 31.1 25.8 30.5 29.9 25 28.4 26.9 23.6 25.7 25.2 25.15 9 31.3 32.7 32.5 27 31.3 30.8 26.4 28.9 28 24.2 26.2 26.2 25 9.5 32 33.6 33.8 28.1 32.1 31.9 27.2 29.9 28.8 25.6 27.2 26.5 25.21 10 32.8 34.9 34.9 28.8 32.8 33 28.6 30.7 30 26.6 28.1 27.6 25.21 10.5 33.4 35.8 35.9 29.2 33.6 34 28.8 31.4 30.7 26.7 29 28.6 25.16 11 34.2 36.9 37.3 30.3 35.7 35 29.4 32 31.6 27.5 29.6 29.5 25.29 11.5 34.6 37.5 38.1 30.7 36.2 36.1 30 32.7 32.8 28.2 30.6 30.7 25.39 12 35.1 38.3 39.3 31.2 36.7 36.7 30.5 32.7 33.6 28.7 31.4 31.2 25.33 12.5 35.4 38.9 40.2 31.6 37.3 37.7 30.8 33.3 34.3 29.3 31.8 32.1 24.99 13 35.4 39.4 41.1 32.2 37.8 38.2 31.3 33.8 35 29.5 32.5 32.8 25.3 13.5 35.5 39.7 41.6 32.9 37.6 38.9 32.1 34.4 35.6 30.3 33 33 25.06 14 35.9 40.2 42.5 33.6 38.2 39.3 32.1 34.8 36 31.1 33.2 33.6 25.28 14.5 36.3 40.4 43.2 34.4 38.2 40 32.5 35.1 36.2 30.7 33.5 34.2 25.33 15 36.2 40.2 43.2 34.7 38.3 40.3 32.8 35.3 36.7 31 33.8 34.9 25.33 15.5 36.2 40.8 43.9 34.8 38.4 40.9 33 35.7 37.3 31.4 34 35.3 25.15 16 36.4 40.9 43.9 34.9 38.2 41.3 33.2 36.2 37.4 31.4 34.5 35.7 25.22 16.5 36.7 41.2 43.9 34.9 38.3 40.9 33.4 36.1 37.6 32 34.7 36 24.95 17 36.9 40.9 43.9 35.3 38.3 40.8 33.5 36.1 38.3 32.2 34.8 36.4 24.8
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17.5 36.9 40.9 43.9 35.5 38.3 40.6 33.6 36.4 38.9 32.3 34.9 36.8 25.12 18 36.6 40.9 43.9 35.2 38.2 40.3 33.8 36.2 39.3 32.3 34.9 37 24.9 18.5 36.6 40.6 43.8 35.2 38.2 40.4 33.8 36 38.8 32.4 34.9 37.2 25.15 19 36.5 40.6 43.8 35.1 38.1 40.5 32.7 35.7 38.7 32.3 34.9 37.3 24.96 19.5 36.5 40.5 43.9 35.1 38.1 40.5 32.5 35.6 38.7 32.3 35 37.1 25.14 20 36.5 40.5 43.7 35 37.9 40.4 32.3 35.6 38.4 32.3 35 37.2 25.32 20.5 36.4 40.3 43.7 35.1 37.8 40.4 31.8 35.5 38.1 32 35 37.1 25.03 21 36.3 40.2 43.6 34.9 37.8 40.3 31.6 35.5 37.7 32.1 34.8 37 25.28 21.5 36.3 39.8 43.6 34.8 37.8 40.4 31.1 35.3 37.6 31.9 34.7 36.9 25.39 22 36.2 39.7 43.2 34.7 37.6 40.3 30.8 35.3 37.4 31.5 34.7 36.8 25.15 22.5 36.1 39.6 43.1 34.8 37.6 40.2 30.4 35.2 37.1 31 34.6 36.4 25.21 23 35.8 39.6 42.7 34.6 37.5 40.2 30.4 35.1 37 30.7 34.4 36.3 25.02 23.5 35.3 39.4 41.5 34.1 36.9 39.7 30.5 35.1 36.7 30 34.3 36.1 25.37 24 34.9 39.2 41.2 34 36.3 39.5 30.3 34.4 36.1 29.4 33.9 35.4 25.25 26 33.9 38.7 40.7 33.6 35.2 38.7 29.6 33.1 35.4 28.8 33 34.3 25.48 28 33.5 38.1 40.2 33.2 34.7 37.9 29.1 32.5 35 28 32.4 33.6 25.21
Table B.2 Semi Adiabatic Temperature Rise Data at Average Ambient Temperature of 35.64 0C
Mixture Code Amb. Hour BA-0 BA-6.5 BA-13 BA-20 Temp T M B T M B T M B T M B 0.5 20 21.2 21.6 19.6 20.4 21 15.9 18.5 19.2 19.5 19.6 19.5 35.01 1 20.6 21.3 21.7 20.3 20.6 21.2 20 19.9 19.9 19.4 19.6 19.5 35.17 1.5 21.1 21.9 21.8 21.1 20.7 21.2 20.4 20.1 20.1 19.8 19.7 19.6 34.85 2 22.1 22.1 22.1 22.2 21.1 21.5 20.4 20.2 20.2 19.8 19.8 19.6 35.38 2.5 23.1 22.6 22.3 22.6 21.4 21.7 20.7 20.7 20.4 19.3 19.9 19.9 35.40 3 23.5 23 22.3 23.4 21.6 22 21.9 21.3 20.8 19.4 20.2 20.1 35.27 3.5 23.6 24.1 22.7 23.5 22.2 22.1 22.4 21.7 21.1 19.9 20.5 20.3 35.45 4 24.8 25.3 23.2 23.9 22.3 22.5 23 22.1 21.6 20.5 20.6 20.3 35.51 4.5 25.8 25.5 23.9 24.4 22.7 23.2 23.6 22.5 22.1 20.9 21.2 20.9 35.47 5 26.8 26.2 25.5 25.5 24.2 23.8 24 23.1 22.8 21.1 22.6 21.3 35.22 5.5 27.9 26.5 25.8 26.6 24.9 24.6 24.7 23.7 23.4 22.3 22.9 21.9 35.43 6 29 27.7 26.8 27.8 26.2 25.2 25.3 24.5 23.9 23.3 23.4 22.1 35.90 6.5 30.2 29.3 28.1 29.1 26.4 26.3 26.2 25.2 24.5 24.5 24 23.1 35.59 7 30.9 30.2 29 30.3 27.7 27.3 26.8 25.8 25.3 25.6 24.8 23.7 35.39 7.5 31.8 31.5 30.3 30.7 29.3 28.2 27.7 26.3 26.7 26.8 25.3 24.1 35.54 8 32.5 32.3 31.3 31.4 30.2 28.9 28.4 26.8 27.2 27.1 25.5 24.5 35.43 8.5 33.2 33.3 32.3 32.2 31.7 30.2 29.9 28.1 28 27.8 26.7 25.1 35.60 9 33.8 34.5 33.6 33 32.6 31.3 30.6 29 28.7 28.9 27.4 25.9 36.00 9.5 34.4 35.4 34.7 33.6 33.7 32.3 31.3 30.4 29.2 30.2 28.7 26.6 35.66
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10 35.4 36.6 36 34.2 34.9 33.6 32.1 31 30.4 31 29 27.5 36.03 10.5 36 37.4 36.8 34.7 35.6 34.6 32.8 32.3 31.3 31.7 30.9 28.8 35.42 11 36.8 38.6 38.2 35.4 36.3 35.5 33.2 33.4 32.6 33 31.9 29.4 35.75 11.5 36.7 39.2 39.2 35.8 36.9 36.4 33.6 34.1 34.1 33.6 32.6 30.9 35.62 12 37.1 40 40.1 36.1 37.4 37.1 34.2 35.7 35.4 33.9 33.5 31.7 35.23 12.5 37.6 40.8 41.2 36.6 38 38 34.6 36.2 36.6 34.1 33.9 32.5 35.65 13 37.6 41.9 42.7 37 38.6 38.7 35.2 37.1 37.8 34.5 34.6 33.2 35.95 13.5 37.7 42.3 43.3 37.1 38.8 40.7 35.6 37.5 38.6 34.7 35 34.6 35.58 14 37.8 42.7 43.9 37.2 39.4 41.3 36.1 38.3 38.9 34.9 35.3 35 35.83 14.5 38.2 43 44.5 37.2 40.2 42 36.3 39.1 39.1 35 35.5 36.1 35.80 15 38.1 43.4 45.8 37.2 40.5 42.5 36.4 39.4 39.6 35.1 35.8 36.9 35.80 15.5 37.9 43.7 46.2 37.3 41.6 42.8 36.6 39.9 40.3 35.1 36.3 37.3 35.78 16 37.8 43.4 46.8 37.3 41.8 43.1 36.7 40 40.9 35.1 36.8 37.9 35.34 16.5 37.7 43.5 47 37.3 42.1 44.6 36.7 40.2 41.2 35.1 37.5 38.3 35.29 17 37.7 43.5 47 37.1 42.2 44.6 36.6 40.2 41.7 35.2 38 38.6 35.87 17.5 37.7 43.5 46.9 37.1 42 45.1 36.5 39.6 42 35.1 38.2 39.1 35.76 18 37.6 43.5 46.9 37.1 42 45.3 36.3 39.6 42.4 35.1 38.3 39.6 35.82 18.5 37.5 43.4 46.8 37 42 45 36.3 39.7 42.7 35 38.9 40.3 35.58 19 37.5 43.4 46.6 37 42 45.1 36.2 39.8 42.7 34.9 38.9 40.9 36.00 19.5 37.5 43.3 46.6 37 41.9 45 36.2 39.8 42.6 34.9 38.8 41.3 35.78 20 37.4 43.2 46.4 36.9 41.8 44.9 36 39.6 42.6 34.5 38.8 41.4 35.90 20.5 37.4 43.1 46.4 36.7 42 44.8 35.8 39.7 42.6 34.4 38.8 41.4 35.59 21 37.4 43 46.2 36.6 41.8 44.8 35.8 39.6 42.5 34.2 38.7 41.3 35.86 21.5 37.3 42.8 46.1 36.4 41.7 44.7 35.6 39.5 42.2 34.2 38.6 41.4 35.81 22 37.2 42.8 46.2 36.5 41.7 44.6 35.5 39.5 42.1 34 38.4 41.3 35.98 22.5 37.1 42.7 46.2 36.4 41.5 44.3 35.3 39.3 42.1 34 38.3 41.3 36.02 23 37.1 42.6 46.1 36.1 41.6 44.2 35.3 39.3 41.9 33.9 38.2 41.2 36.09 23.5 37.1 42.3 46.1 36.1 41.6 44.1 35.1 39.2 41.8 33.9 38.2 41.1 35.79 24 37.1 41.8 46.1 36 41.5 44 35.1 39 41.6 33.9 38 40.8 36.09 26 36.5 41.2 45.9 35.9 41.3 44 35 38.8 41.5 33.9 37.9 40.7 36.09 28 36.4 41.1 45.7 35.7 41 43.8 34.8 38.6 41.4 33.9 37.8 40.3 35.80
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Table B.3 Semi Adiabatic Temperature Rise Data at Average Ambient Temperature of 43.770 C
Mixture Code Amb. Hour BA-0 BA-6.5 BA-13 BA-20 Temp T M B T M B T M B T M B 0.5 19.8 21.2 21.3 20.1 20.8 20.7 20.5 20.9 20.1 20.5 20.5 20.1 43.59 1 20.3 21.4 21.4 20.2 20.9 21.2 20.4 21.2 20.8 20.8 20.6 20.6 43.46 1.5 20.9 22.5 21.7 20.3 21 21.6 20.6 21.9 21.1 21.4 20.7 20.5 42.30 2 22.1 22.7 21.9 20.7 21.3 21.8 21 22.3 21.6 21.7 21 20.9 43.23 2.5 24.2 23.6 22.1 21.2 21.9 21.9 21.3 22.5 21.9 22 21.6 21.1 44.28 3 25.1 24.6 22.9 21.8 22.8 22.1 21.7 22.9 22.1 22.2 21.8 21.6 42.93 3.5 25.9 25.5 24.1 22.6 23.1 22.4 22.2 22.6 22.4 22.5 22.2 21.8 42.71 4 27.6 26.6 25.3 24.4 23.9 22.7 23.3 23 22.7 22.8 22.7 22.4 43.32 4.5 28.3 27.8 26.7 24.6 24.3 23 23.8 23.6 22.9 23.5 23.2 23 43.55 5 29.4 28.2 27.4 25.2 25 23.8 24.2 24.1 23.5 24.6 23.8 23.6 43.81 5.5 30.2 29 28.9 26.2 26.3 24.2 25.8 25.3 23.7 25.2 24.6 23.9 43.67 6 30.9 30.8 29.7 27.4 26.8 24.9 26.8 26.6 24.1 26.2 25 24.1 43.63 6.5 31.7 31.2 30.4 28 27.8 25.5 27.7 27.1 24.6 27.4 25.8 24.8 43.97 7 32.2 32.1 31.1 29.6 28.8 26.1 28.1 27.5 25.2 28 25.9 25.5 43.80 7.5 33.3 33.3 31.8 30.8 30.7 27.4 29.2 28.2 26.2 28.8 26.3 26.3 43.67 8 33.9 34.2 32.3 31.6 31.9 28.9 30.6 29 27 30.3 26.8 26.9 43.02 8.5 34.7 35.4 33.2 32.6 33 29.4 31.8 30.7 27.9 31.8 27.3 27.4 43.15 9 35.4 36.3 34.9 33.3 34.2 30.7 32.5 31.8 28.4 32.8 28.3 28.1 44.07 9.5 36.1 37.7 35.7 34.5 35 31.4 33.4 32.6 29.6 33.5 29 28.8 44.22 10 37.3 39.2 36.2 35.3 36.3 32.9 34.9 33.2 31 34.7 29.9 29.6 44.28 10.5 38.7 40.6 37.4 36.8 38 34 35.5 34.7 32 35.5 30.5 30.7 44.22 11 40.5 41.3 38.6 38.2 38.7 35.9 36 35.2 33.7 36.5 31 31.2 43.62 11.5 41.4 41.5 40.2 38.4 39.5 36.7 36.7 36.6 34.6 36.9 32.2 32.6 44.21 12 42.9 42.5 41.7 39.9 39.9 38.3 37.2 37.4 35.2 37.1 32.7 33.3 44.63 12.5 43.3 44.2 43.8 40.3 40.6 39.2 37.7 38.2 36 37.6 33.2 34.7 43.41 13 44.5 45.7 44.8 41.4 40.7 40.2 38.9 38.9 37.6 37.8 33.6 35.7 44.17 13.5 45.6 46.2 46 42.1 40.8 40.9 39.7 39.5 38.1 38.2 34.5 36.2 44.17 14 45.9 46.8 46.7 42.9 41.4 41.5 40.8 39.6 39 38.6 35.3 37 44.31 14.5 46.2 47.9 46.9 43.8 42.6 42.8 41.3 40.1 40 38.8 36.6 38.6 43.58 15 46.9 47.9 48.3 44.2 43.3 43.7 41.7 40.8 40.9 39.2 37.3 39.4 43.58 15.5 47.2 48.3 49 44.9 43.6 44.2 42.4 41.2 41.3 39.5 38.8 41.1 43.25 16 47.3 48.6 49.4 45.1 43.8 45.3 42.5 41.9 42.1 39.8 38.9 41.3 43.65 16.5 47.3 48.7 49.7 45.2 44.4 46 42.6 42.2 43 39.9 39.4 41.7 44.28 17 47.3 48.8 50.1 45.3 44.7 46.3 43 42.8 43.2 39.9 40 42.1 43.58 17.5 47.5 48.8 50.5 45.4 45.2 46.5 43.1 43.2 44.3 39.9 40.5 42.6 44.17 18 47.4 48.8 50.7 45.4 45.5 46.8 43.1 43.7 44.6 39.9 40.7 42.6 43.38 18.5 47.4 48.9 51 45.4 45.6 47.2 43.1 44 44.9 39.8 40.8 42.9 43.40
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19 47.4 48.8 51.3 45.5 45.7 47.6 43.1 44.4 45.1 39.8 40.8 43 43.58 19.5 47.4 48.8 51.2 45.3 45.7 47.7 43.3 44.6 45.3 39.8 40.8 43 43.08 20 47.3 48.7 51.3 45.3 45.8 48.1 43.5 44.5 45.6 39.8 40.7 42.9 43.29 20.5 47.3 48.7 51.3 45.2 46 48.5 43.4 44.5 45.7 39.9 40.7 42.9 43.66 21 47.2 48.7 51.4 45 46.1 48.6 43.4 44.6 46.1 39.8 40.7 42.8 44.14 21.5 47.2 48.6 51.4 44.9 46.1 48.6 43.3 44.8 46.3 39.7 40.7 42.7 44.76 22 47.2 48.6 51.4 44.9 46.1 48.7 43.3 44.8 46.2 39.6 40.8 42.7 44.88 22.5 47.2 48.6 51.3 44.6 46 48.7 43.2 44.8 46.3 39.5 40.7 42.8 44.52 23 47.1 48.6 51.3 44.5 45.9 48.6 43.1 44.6 46.4 39.5 40.7 42.7 44.81 23.5 47 48.5 51.2 44.4 45.8 48.5 43 44.5 46.2 39.4 40.6 42.6 44.10 24 47.1 48.5 51.1 44.4 45.7 48.4 42.9 44.5 46.2 39.4 40.5 42.5 43.50 26 47 48.3 51 44 45.4 48.2 42.7 44.2 45.8 39.4 40.4 42.3 44.41 28 46.9 48.1 51 43.6 45.1 48 42.4 44 45.6 39.3 40.1 42.1 43.59
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Early Age Thermal Behavior of Bagasse ash Concrete Under Different Ambient Temperatures
APPENDIX C
CHEMICAL PROPERTY OF BAGASSE ASH AND CEMENET
Table C.1 Chemical Property of Bagasse Ash
Table C.2 Chemical Property of Cement
MSc Thesis Page 84